need solution

(4) (3 + 3 + 3 + 4 + 4 + 3 pts) A zipcode is a sequence of five digits from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. For example, the following are some of the zipcodes: 00110, 33333, 00000, and 98765. An odd digit is one of 1, 3, 5, 7, 9; the rest are even digits. How many zipcodes are possible (a) if there are no restrictions? (b) if the digits must be distinct (i.e. no two digits are the same)? (c) if the first two digits are the same? (d) if either the first digit is odd or the last digit is odd? (e) if at least one of the digits is odd? (f) if the digits, when read left to right, are strictly decreasing in value (for example, 96421)? (Hint: pick the digits first, and then ...)