A buying order for a retail store like Amazon.com or Walmart has a list of items, each with its name, quantity, price, and the sales tax rate. Here is an example:

ID    Description                   Quantity    Price    Tax rate
B003 C++ Programming CD       2          30.5    3.5%
A001 iPhone 6 Plus                      1          700       7%
A002 Macbook Pro                      1          800       7%

Task 1. Declare a struct OrderItem to help store information for an item in an order.

Task 2. Declare a class Order (within the submitted cpp file) with the following requirements:

a. Have an array of OrderItem structs to store the items of an order. Since the number of ordered items in an order varies, and this class should have a field to store that number and the array of OrderItem should be a dynamic array.

b. Have two methods to load and save the order to a CSV (comma-separated values) file. Their prototypes are
void loadCSV(char *filename);
void saveCSV(char *filename);

For example, the previous order will be saved as a CSV file with the following content:
ID,Description,Quantity,Price,Tax
B003,C++ Programming CD,2,30.5,3.5%
A001,iPhone 6 Plus,1,700,7%
A002,Macbook Pro,1,800,7%

Hint: When loading an order from a CSV file, you should read it quickly to determine the number of items. Then you can allocate the array of OrderItem with size given by that number. Finally you re-read the file and parse each line as an item in that array.

c. Have a method to compute the total of an order, including taxes. For example, the previous order has the total of
2 * 30.5 * (1 + 0.035) + 1 * 700 * (1 + 0.07) + 1 * 800 * (1 + 0.07) = 1668.135
Its prototype is:
double computeTotal()

d. Have a method to update the quantity of an item in an order. Its prototype is
void updateQuantity(string itemID, int quantity)

For example, if the shopper decides to buy one C++ Programming CD rather than two, this function will be called by:
order.updateQuantity("B003", 1);

This function should compare the old quantity and the new quantity and print out an error message if they are the same.

Task 3. Write a main() function to test your code. The testing procedure is as the following:
1 Load the order from a CSV file.
2 Compute the total and compare it with your pre-computed value.
3 Update quantity of two different items in the order.
4 Save the updated order to another CSV file and manually check that file.

You will create at least two CSV files for this (Hint: You could use Excel to create them and pre-compute the totals). Remember to attach those two CSV files as comments in the submitted cpp file.

A buying order for a retail store like Amazon.com or Walmart has a...