a. How many 3-digit numbers can you make using the digits from
the set of (3, 4, 5, 6, 8, 2, 7) without repetitions?
b. How many numbers can be made with the digits from the set of
(0, 3, 5, 7, 8, 4, 9), which are greater than 0 and less than a
thousand (repetitions are allowed)?