Two cars collide inelastically and stick together after the collision. Before the collision, the magnitudes of their momenta are P1 and P2. After the collision, what is the magnitude of their combined momentum?
a) P1 + P2
b) P1 - P2
c) P2 - P1
d) √(P1P2)
e) 1/2(P1 + P2)
f) √(P1 + P2)
g) The answer depends on the directions in which the cars were moving before the collision.