A Test Rocket Is Fired Straight Up from Rest with a Net

Multiple Choice

A test rocket is fired straight up from rest with a net acceleration of 20.0 m/s².After 4.00 seconds the motor turns off,but the rocket continues to coast upward with no appreciable air resistance.What maximum elevation does the rocket reach?

A) 487 m
B) 327 m
C) 320 m
D) 408 m
E) 160 m