diff --git a/orderBook.js b/orderBook.js
new file mode 100644
index 0000000..baec02f
--- /dev/null
+++ b/orderBook.js
@@ -0,0 +1,43 @@
+function reconcileOrder(existingBook, incomingOrder) {
+  let updatedBook = [];
+  let changedOrders = [];
+
+  if (!existingBook.length) {
+    updatedBook.push(incomingOrder);
+
+    return updatedBook;
+  }
+
+  for (let i = 0; i < existingBook.length; i++) {
+    if (
+      existingBook[i].type !== incomingOrder.type &&
+      existingBook[i].price === incomingOrder.price &&
+      existingBook[i].quantity === incomingOrder.quantity
+    ) {
+      incomingOrder.price = -1;
+    } else if (
+      existingBook[i].type !== incomingOrder.type &&
+      existingBook[i].price === incomingOrder.price &&
+      existingBook[i].quantity !== incomingOrder.quantity
+    ) {
+      if (existingBook[i].quantity > incomingOrder.quantity) {
+        existingBook[i].quantity =
+          existingBook[i].quantity - incomingOrder.quantity;
+        incomingOrder.quantity = 0;
+        changedOrders.push(existingBook[i]);
+      } else {
+        incomingOrder.quantity =
+          incomingOrder.quantity - existingBook[i].quantity;
+      }
+    } else {
+      updatedBook.push(existingBook[i]);
+    }
+  }
+  if (incomingOrder.price !== -1 && incomingOrder.quantity !== 0) {
+    updatedBook.push(incomingOrder);
+  }
+  return updatedBook.concat(changedOrders);
+}
+module.exports = {
+  reconcileOrder,
+};
diff --git a/tests.js b/tests.js
index 4926c8a..a2a8090 100644
--- a/tests.js
+++ b/tests.js
@@ -1,116 +1,163 @@
 /* eslint-disable max-len */
-const { expect } = require('chai')
-const reconcileOrder = require('./orderBook')
+const { expect } = require("chai");
+const { reconcileOrder } = require("./orderBook");
 
-describe('Order Book', () => {
-  describe('reconcileOrder', () => {
-    it('adds an order to the book when the book is empty and thus cannot fulfill the order', () => {
-      const existingBook = []
-      const incomingOrder = { type: 'sell', quantity: 10, price: 6150 }
+describe("Order Book", () => {
+  describe("reconcileOrder", () => {
+    it("adds an order to the book when the book is empty and thus cannot fulfill the order", () => {
+      const existingBook = [];
+      const incomingOrder = { type: "sell", quantity: 10, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 10, price: 6150 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 10, price: 6150 },
+      ]);
+    });
 
-    it('adds an order to the book when the book has orders of the corresponding type (i.e. a sell with no buys)', () => {
-      const existingBook = [{ type: 'sell', quantity: 10, price: 6150 }]
-      const incomingOrder = { type: 'sell', quantity: 12, price: 6000 }
+    it("adds an order to the book when the book has orders of the corresponding type (i.e. a sell with no buys)", () => {
+      const existingBook = [{ type: "sell", quantity: 10, price: 6150 }];
+      const incomingOrder = { type: "sell", quantity: 12, price: 6000 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
       expect(updatedBook).to.deep.equal([
-        { type: 'sell', quantity: 10, price: 6150 },
-        { type: 'sell', quantity: 12, price: 6000 }
-      ])
-    })
+        { type: "sell", quantity: 10, price: 6150 },
+        { type: "sell", quantity: 12, price: 6000 },
+      ]);
+    });
 
-    it('adds an order to the book when the book has a corresponding order type but it does not match', () => {
-      const existingBook = [{ type: 'buy', quantity: 10, price: 6000 }]
-      const incomingOrder = { type: 'sell', quantity: 12, price: 6150 }
+    it("adds an order to the book when the book has a corresponding order type but it does not match", () => {
+      const existingBook = [{ type: "buy", quantity: 10, price: 6000 }];
+      const incomingOrder = { type: "sell", quantity: 12, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
       expect(updatedBook).to.deep.equal([
-        { type: 'buy', quantity: 10, price: 6000 },
-        { type: 'sell', quantity: 12, price: 6150 }
-      ])
-    })
+        { type: "buy", quantity: 10, price: 6000 },
+        { type: "sell", quantity: 12, price: 6150 },
+      ]);
+    });
 
-    it('fulfills an order and removes the matching order when the book contains a matching order of the same quantity', () => {
-      const existingBook = [{ type: 'buy', quantity: 10, price: 6150 }, { type: 'sell', quantity: 12, price: 6250 }]
-      const incomingOrder = { type: 'sell', quantity: 10, price: 6150 }
+    it("fulfills an order and removes the matching order when the book contains a matching order of the same quantity", () => {
+      const existingBook = [
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "sell", quantity: 12, price: 6250 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 10, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 6250 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 6250 },
+      ]);
+    });
 
-    it('fulfills an order and reduces the matching order when the book contains a matching order of a larger quantity', () => {
-      const existingBook = [{ type: 'buy', quantity: 15, price: 6150 }, { type: 'sell', quantity: 12, price: 6950 }]
-      const incomingOrder = { type: 'sell', quantity: 10, price: 6150 }
+    it("fulfills an order and reduces the matching order when the book contains a matching order of a larger quantity", () => {
+      const existingBook = [
+        { type: "buy", quantity: 15, price: 6150 },
+        { type: "sell", quantity: 12, price: 6950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 10, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 6950 }, { type: 'buy', quantity: 5, price: 6150 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 6950 },
+        { type: "buy", quantity: 5, price: 6150 },
+      ]);
+    });
 
-    it('partially fulfills an order, removes the matching order and adds the remainder of the order to the book when the book contains a matching order of a smaller quantity', () => {
-      const existingBook = [{ type: 'buy', quantity: 10, price: 6150 }, { type: 'sell', quantity: 12, price: 5950 }]
-      const incomingOrder = { type: 'sell', quantity: 15, price: 6150 }
+    it("partially fulfills an order, removes the matching order and adds the remainder of the order to the book when the book contains a matching order of a smaller quantity", () => {
+      const existingBook = [
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "sell", quantity: 12, price: 5950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 15, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 5950 }, { type: 'sell', quantity: 5, price: 6150 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 5950 },
+        { type: "sell", quantity: 5, price: 6150 },
+      ]);
+    });
 
-    it('uses two existing orders to completely fulfill an order, removing the matching orders from the book', () => {
-      const existingBook = [{ type: 'buy', quantity: 10, price: 6150 }, { type: 'buy', quantity: 5, price: 6150 }, { type: 'sell', quantity: 12, price: 5950 }]
-      const incomingOrder = { type: 'sell', quantity: 15, price: 6150 }
+    it("uses two existing orders to completely fulfill an order, removing the matching orders from the book", () => {
+      const existingBook = [
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "buy", quantity: 5, price: 6150 },
+        { type: "sell", quantity: 12, price: 5950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 15, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 5950 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 5950 },
+      ]);
+    });
 
-    it('uses two existing orders to completely fulfill an order, removing the first matching order from the book and reducing the second', () => {
-      const existingBook = [{ type: 'buy', quantity: 10, price: 6150 }, { type: 'buy', quantity: 10, price: 6150 }, { type: 'sell', quantity: 12, price: 6950 }]
-      const incomingOrder = { type: 'sell', quantity: 15, price: 6150 }
+    it("uses two existing orders to completely fulfill an order, removing the first matching order from the book and reducing the second", () => {
+      const existingBook = [
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "sell", quantity: 12, price: 6950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 15, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 6950 }, { type: 'buy', quantity: 5, price: 6150 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 6950 },
+        { type: "buy", quantity: 5, price: 6150 },
+      ]);
+    });
 
-    it('uses two existing orders to partially fulfill an order, removing the matching orders from the book and reducing the incoming order before adding it to the book', () => {
-      const existingBook = [{ type: 'buy', quantity: 10, price: 6150 }, { type: 'buy', quantity: 10, price: 6150 }, { type: 'sell', quantity: 12, price: 6950 }]
-      const incomingOrder = { type: 'sell', quantity: 25, price: 6150 }
+    it("uses two existing orders to partially fulfill an order, removing the matching orders from the book and reducing the incoming order before adding it to the book", () => {
+      const existingBook = [
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "buy", quantity: 10, price: 6150 },
+        { type: "sell", quantity: 12, price: 6950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 25, price: 6150 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 6950 }, { type: 'sell', quantity: 5, price: 6150 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 6950 },
+        { type: "sell", quantity: 5, price: 6150 },
+      ]);
+    });
 
-    it.skip('Extra Credit: it fulfills a mismatched order when both parties benefit', () => {
-      const existingBook = [{ type: 'buy', quantity: 15, price: 6000 }, { type: 'sell', quantity: 12, price: 6950 }]
-      const incomingOrder = { type: 'sell', quantity: 15, price: 5900 }
+    it.skip("Extra Credit: it fulfills a mismatched order when both parties benefit", () => {
+      const existingBook = [
+        { type: "buy", quantity: 15, price: 6000 },
+        { type: "sell", quantity: 12, price: 6950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 15, price: 5900 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
-      expect(updatedBook).to.deep.equal([{ type: 'sell', quantity: 12, price: 6950 }])
-    })
+      expect(updatedBook).to.deep.equal([
+        { type: "sell", quantity: 12, price: 6950 },
+      ]);
+    });
 
-    it.skip('Extra Credit: it does not fulfill a mismatched order when it does not benefit both parties', () => {
-      const existingBook = [{ type: 'buy', quantity: 15, price: 5900 }, { type: 'sell', quantity: 12, price: 6950 }]
-      const incomingOrder = { type: 'sell', quantity: 15, price: 6000 }
+    it.skip("Extra Credit: it does not fulfill a mismatched order when it does not benefit both parties", () => {
+      const existingBook = [
+        { type: "buy", quantity: 15, price: 5900 },
+        { type: "sell", quantity: 12, price: 6950 },
+      ];
+      const incomingOrder = { type: "sell", quantity: 15, price: 6000 };
 
-      const updatedBook = reconcileOrder(existingBook, incomingOrder)
+      const updatedBook = reconcileOrder(existingBook, incomingOrder);
 
       expect(updatedBook).to.deep.equal([
-        { type: 'buy', quantity: 15, price: 5900 },
-        { type: 'sell', quantity: 12, price: 6950 },
-        { type: 'sell', quantity: 15, price: 6000 },
-      ])
-    })
-  })
-})
+        { type: "buy", quantity: 15, price: 5900 },
+        { type: "sell", quantity: 12, price: 6950 },
+        { type: "sell", quantity: 15, price: 6000 },
+      ]);
+    });
+  });
+});