Step $5$: Implement the menu options

Step $5$a: In the main section of the code, call print$\_$menu$()$ and prompt for the user's choice of menu options. Each option is represented by a single character.

If an invalid character is entered, continue to prompt for a valid choice. When a valid option is entered, execute the option by calling execute$\_$menu$().$ Then, print the menu and prompt for a new option. Continue until the user enters $\text{'}$q$\text{'}.(1$ pt$)$

Hint: Implement Quit before implementing other options.

Ex:

a $-$ Add item to cart r $-$ Remove item from cart c $-$ Change item quantity i $-$ Output items' descriptions o $-$ Output shopping cart q $-$ Quit Choose an option: