There are four different roads between town A and town B, three different roads between town B and town C , and two different roads between town A and town C.

(a) How many different routes are there from A to C altogether?

(b) How many different routes are there from A to C and back(any road can be used once in each direction)?

(c) How many different routes are there from A to C and back in part(b) that visit B at least once?

(d) How many different routes are there from A to C and back in part(b) that do not use any road twice?