Let S = {1, 2, 3, 4, 5, A, B, C, D, E, F, G}. (a) A password from S is to be created and it is to consist of three digits followed by four letters and the letters must all be different (the digits may be repeated). How many passwords are possible? (b) How many 7-element subsets does S have that contain the digits 1 and 2 but do not contain A? (c) How many 5-element subsets are there that contain exactly two digits and three letters? (d) How many subsets has S?