diff --git a/CM2005 Object Oriented Programming/Topic 2/2.5.1/OrderBookEntry.cpp b/CM2005 Object Oriented Programming/Topic 2/2.5.1/OrderBookEntry.cpp
new file mode 100644
index 0000000..d2f3f0e
--- /dev/null
+++ b/CM2005 Object Oriented Programming/Topic 2/2.5.1/OrderBookEntry.cpp	
@@ -0,0 +1,18 @@
+#include "OrderBookEntry.h"
+
+OrderBookEntry::OrderBookEntry
+(
+  double price,
+  double amount,
+  std::string timestamp,
+  std::string product,
+  OrderBookType orderType
+)
+:
+price{price},
+amount{amount},
+timestamp{timestamp},
+product{product},
+orderType{orderType}
+{
+}
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diff --git a/CM2005 Object Oriented Programming/Topic 2/2.5.1/OrderBookEntry.h b/CM2005 Object Oriented Programming/Topic 2/2.5.1/OrderBookEntry.h
new file mode 100644
index 0000000..bd28b8b
--- /dev/null
+++ b/CM2005 Object Oriented Programming/Topic 2/2.5.1/OrderBookEntry.h	
@@ -0,0 +1,23 @@
+#include <string>
+
+enum class OrderBookType
+{
+  bid,
+  ask
+};
+
+class OrderBookEntry
+{
+  public:
+    OrderBookEntry(
+      double price,
+      double amount,
+      std::string timestamp,
+      std::string product,
+      OrderBookType orderType);
+    double price;
+    double amount;
+    std::string timestamp;
+    std::string product;
+    OrderBookType orderType;
+};
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diff --git a/CM2005 Object Oriented Programming/Topic 2/2.5.1/a.exe b/CM2005 Object Oriented Programming/Topic 2/2.5.1/a.exe
new file mode 100644
index 0000000..d5230da
Binary files /dev/null and b/CM2005 Object Oriented Programming/Topic 2/2.5.1/a.exe differ
diff --git a/CM2005 Object Oriented Programming/Topic 2/2.5.1/main.cpp b/CM2005 Object Oriented Programming/Topic 2/2.5.1/main.cpp
new file mode 100644
index 0000000..b7d0484
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+++ b/CM2005 Object Oriented Programming/Topic 2/2.5.1/main.cpp	
@@ -0,0 +1,65 @@
+#include <iostream>
+#include <string>
+#include <vector>
+#include <OrderBookEntry.h>
+
+double computeAveragePrice(std::vector<OrderBookEntry>& entries)
+{
+  double avg = 0;
+  for(unsigned int i=0; i<entries.size(); ++i) //thid doesn't create a copy, ++i increments on the same variable
+  {
+    //std::cout << "The price is " << entries[i].price << std::endl;
+    avg += entries[i].price;
+  }
+  return avg/entries.size();
+}
+
+int main()
+{
+
+  std::vector<OrderBookEntry> orders;
+
+  orders.push_back( OrderBookEntry{
+                                    10000,
+                                    0.002,
+                                    "2020/03/17 17:01:24.884492",
+                                    "BTC/USDT",
+                                    OrderBookType::bid});
+
+  orders.push_back( OrderBookEntry{
+                                    50000,
+                                    0.002,
+                                    "2020/03/17 17:01:24.884492",
+                                    "BTC/USDT",
+                                   OrderBookType::bid});
+
+  // Version 1
+  std::cout << "Version 1" << std::endl;
+  for(OrderBookEntry order : orders) //this create a copy of the members of orders and assigns it to 'order'
+  {
+    std::cout << "The price is " << order.price << std::endl;
+  }
+
+  std::cout << "---new line---" << std::endl;
+
+  for(OrderBookEntry &order : orders) //this doesn't crate a copy
+  {
+    std::cout << "The price is " << order.price << std::endl;
+  }
+
+  // Version 2
+  std::cout << "Version 2" << std::endl;
+  for(unsigned int i=0; i<orders.size(); ++i) //thid doesn't create a copy, ++i increments on the same variable
+  {
+    std::cout << "The price is " << orders[i].price << std::endl;
+  }
+
+  //version 3
+  std::cout << "Version 3" << std::endl;
+  for(unsigned int i=0; i<orders.size(); ++i) //thid doesn't create a copy, ++i increments on the same variable
+  {
+    std::cout << "The price is " << orders.at(i).price << std::endl;
+  }
+
+  std::cout << "Average price: " << computeAveragePrice(orders) << std::endl;
+}
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