Generate a C++ program to sort items of a structs-of-array. Assume that the struct is 

struct invoice 
{
unsigned int custNo;
unsigned short amount;
string owner;
};

Generate an array with 20 invoices, which are randomly initiated with custNO (1000-5000), amount (1-2000 as dollar amount), owner (3-UpperLetter string, such as ABC, COM). Then generatethe Selection Sort algorithm to 

- Sort cities over custNo 

- Sort cities over amount.

- Sort cities over owner.

In a menu selection, user chooses one of these option, or "exit" option to exit the program.