The factors of each term in the expression 24x-60y are shown below.

24x: 1, 2, 3, 4, 6, 8, 12, 24, x
60y: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60, y

What is the greatest common factor of 24x and 60y?