It is done by this formula
combinations = n! / [r! * (n - r)!]
combinations = 15! / [4! * 11!]
combinations = 15 * 14 * 13 * 12 * 11! / [4! * 11!]
combinations = 15 * 14 * 13 * 12 / 4 * 3 * 2
combinations = 15 * 7 * 13
combinations = 1,365
answer is b
