A basketball team has twelve players. The starting lineup of five players must be chosen.

a. In how many ways can the starting five be chosen if no positions are assigned to the players?
b. In how many ways can the starting five be chosen if each player is assigned one of the following positions: center, power forward, small forward, off guard, and point guard?
c. Suppose all twelve players differ in height. In how many ways can the starting five in part b.) be chosen so that the center is taller than the power forward who is taller than the small forward who is taller than the off guard who is taller than the point guard?