A 4.00-kg mass and a 9.00-kg mass are being held at rest against a compressed spring on a frictionless surface. When the masses are released, the 4.00-kg mass moves to the east with a speed of 2.00 m/s. What is the velocity of the 9.00-kg mass after the masses are released?

A) 0.500 m/s east

B) 0.500 m/s west

C) 4.50 m/s west

D) 0.888 m/s west

E) 2.00 m/s west