A Rock Is Propelled Upward from the Top of a Building

Multiple Choice

A rock is propelled upward from the top of a building 270 feet tall at an initial velocity of 168 feet per second. The function that describes the height of the rocket in terms of time t is $( t ) = - 16 t ^ { 2 } + 168 t + 270$ Determine the
Time at which the rock reaches its maximum height.

A) 8.4 sec
B) 10.5 sec
C) 4.2 sec
D) 5.25 sec