Как сделать этот вопрос

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Define class Produce.
•    Private data members :  price (float), total (float) and qty (integer).

•    Public member functions: 
o    Define a default constructor to initialize all data members to zeros.
o    Define function set_input(….) which takes in 2 parameters from main( ) and initializes them to price and qty respectively. Calculate total [price multiply qty].
o    Declare class Bill as a friend.

Define class Bill
•    Private data member : grand_total (float).

•    Public member functions:
o    Define a default constructor to initialize grand_total to zero.
o    Define function display( ) to display grand_total [refer to sample output screen].
o    Define the overloaded += function which adds Produce object’s total to grand_total. In the function, display total also (refer to sample output screen, i.e. subtotal).

In main( ):
•    Declare an object BL of class Bill, and object pd of class Produce.
•    In a do-while loop:
    Prompt user to enter price and quantity
    Using object pd, call set_input (…), passing in user input for price and quantity.
    Using object BL, call the function that overloads the "+=" operator [Hint: pass in object pd as parameter].
    Prompt user on whether or not to continue looping.
•    Using object BL, call function display( ).

Что я уже пробовал:

Я стараюсь, но у меня много проблем, кто-то может мне помочь?

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