There are two set pieces in a theater sitting on platforms with wheels. One is a tree with a mass of 50 kg. It is moving at 3 m/s. The other is a fence with a mass of 30 kg. If the two set pieces have equal momentum, how fast is the fence moving?

A. 3 m/s B. 5 m/s

C. 30 m/s D. 90 m/s