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 projectile is launched upward from the ground with an initial velocity of 90 feet per second, its height h in feet t seconds later is given by the function $h ( t ) = - 16 t ^ { 2 } + 90 t$

A) 11.3 seconds
B) 2.8 seconds
C) 0.2 seconds
D) 5.6 seconds