--> Lines like this one (beginning -->) are added comments.
--> Lines starting "$" are commands

--> Try inputs that explore all cases.

--> First, examples of all the error conditions we check for.

$ make_change
Enter amount owed, amount tendered
0 10
Error:  amount owed must be > 0

$ make_change
Enter amount owed, amount tendered
10 0
Error:  amount tendered must be > 0

$ make_change
Enter amount owed, amount tendered
20 10
Error:  amount tendered must be >= amount owed

--> Now a "boundary condition", amounts equal.

$ make_change
Enter amount owed, amount tendered
20 20
Change due is 0
	0 quarters
	0 dimes
	0 nickels
	0 pennies

--> Now a really simple case.

$ make_change
Enter amount owed, amount tendered
18 20
Change due is 2
	0 quarters
	0 dimes
	0 nickels
	2 pennies

--> More "boundary conditions" -- 5 cents should be 1 nickel, no
--> 	5 pennies, etc.

$ make_change
Enter amount owed, amount tendered
20 25
Change due is 5
	0 quarters
	0 dimes
	1 nickels
	0 pennies

$ make_change
Enter amount owed, amount tendered
15 25
Change due is 10
	0 quarters
	1 dimes
	0 nickels
	0 pennies

$ make_change
Enter amount owed, amount tendered
25 50
Change due is 25
	1 quarters
	0 dimes
	0 nickels
	0 pennies

--> Now some "general cases".

$ make_change
Enter amount owed, amount tendered
24 50
Change due is 26
	1 quarters
	0 dimes
	0 nickels
	1 pennies

$ make_change
Enter amount owed, amount tendered
45 100
Change due is 55
	2 quarters
	0 dimes
	1 nickels
	0 pennies