Write the numCombinations method below. Assume that factorial works as specified, regardless of what you wrote in part (a). You must use factorial appropriately to receive full credit. /** Precondition: n and r are between 1 and 12, inclusive. * Determines the number of ways r items can be selected * from n choices and prints the result, as described in part (b). */ public static void numCombinations(int n, int r)