3.28: 5-digit codes less than 60 000
A 5-digit code is to be formed using 5 different numbers selected from 1, 2, 3, 4, 5, 6, 7, 8. Find how many possible codes there are if the code forms
(a)[3]
a number less than 60 000 that ends in a multiple of 3.
(b)[3]
an even number less than 60 000.