Program 5.1

Good evening I need help with my coding. Here is the assignment: Write a program that operates like a cashier terminal in an auto parts store. It begins by prompting for the number of different items being purchased and then starts a loop. In the loop, the program should prompt for the item description, part number, price and quantity of each item being purchased. These four values should be passed as arguments to a custom function that is defined in a separate module file. The imported function should print the subtotal for the item and return it to main. The total should be printed in main after the loop ends. Input prompts (including the programmatic sequential numbering of items) and output should be formatted as in the example output. I have post screenshot of the assignment and what I have done so far. I don't understand why my variable isn't being used when I want to use it. I don't understand the purpose of having varibles not being used. Any ideas?