Find All Fixed Points for the Function by Setting the Function

Multiple Choice

Find all fixed points for the function by setting the function equal to x and solving the resulting equation for x.
-If a ball is thrown upward from the ground with an initial velocity of 128 feet per second, its height after t seconds is given by the function $h ( t ) = - 16 t ^ { 2 } + 128 t$

A) 4 seconds
B) 8 seconds
C) 112 seconds
D) 64 seconds