Consider four-digit numbers that consist of 0, 1, 2, 5, 6, and
9.
a) How many four-digit numbers can be formed from the digits 0, 1,
2, 5, 6, and 9 if each digit can be used
only once? (the four-digit numbers can't start with 0).
b) How many of those four-digit numbers are even?
c) How many are greater than 2200?