Any clues on how many combinations there are here?

#1
Laura is training for a week-long mountain cycling tour. She has 12 short hilly routes from which to choose mid-week rides.
a) How many ways can she choose 4 different rides from the list for the first week's training if order matters?
b) How many ways can she choose 4 different rides if order does not matter?
c) If she has chosen the first weeks rides, how many ways can she choose four more different rides for the second week? Assume that order does not matter.
 
#2
If I remember correctly.

a) 12 * 11 * 10 * 9 = 11880

b) (12 * 11 * 10 * 9)/ 4! = 12 * 11 * 10 * 9)/ (4+3+2+1) = 1188

c) (8 * 7 * 6 * 5)/(4+3+2+1) = 168