diff --git a/CM2005 Object Oriented Programming/Topic 4/4.4.11/OrderBook.cpp b/CM2005 Object Oriented Programming/Topic 4/4.4.11/OrderBook.cpp
index ce9d857..da8a2af 100644
--- a/CM2005 Object Oriented Programming/Topic 4/4.4.11/OrderBook.cpp	
+++ b/CM2005 Object Oriented Programming/Topic 4/4.4.11/OrderBook.cpp	
@@ -1,6 +1,7 @@
 #include "OrderBook.h"
 #include "CSVReader.h"
 #include <map>
+#include <algorithm>
 
 /* Construct, reading a csv data file */
 OrderBook::OrderBook(std::string filename)
@@ -88,4 +89,10 @@ std::string OrderBook::getNextTime(std::string timestamp)
     next_timestamp = orders[0].timestamp;
   }
   return next_timestamp;
+}
+
+void OrderBook::insertOrder(OrderBookEntry& order)
+{
+  orders.push_back(order);
+  std::sort(orders.begin(), orders.end(), OrderBookEntry::compareByTimestamp);
 }
\ No newline at end of file