A Model Rocket Is Launched from a Raised Platform at a Speed

Multiple Choice

A model rocket is launched from a raised platform at a speed of 144 feet per second. Its height in feet is given by $h ( t ) = - 16 t ^ { 2 } + 144 t + 20$ (t = seconds after launch) . After how many seconds does the object reach its maximum height?

A) 2.25 seconds
B) 20 seconds
C) 4.5 seconds
D) 6.5 seconds