Having trouble these problems

Question

The height of a rocekt that is launched is modeled by the function h(t)=−4.9t2+1200t+320h(t)=-4.9t2+1200t+320 where the height is meters above sea level, tt seconds after launch.

a) (2 pts) What is the maximum height the rocket reachers? (Round your answer to two decimal places if necessary.)

   Select an answer meters seconds seconds per meter meters per second 

b) (2 pts) At what time does the rocket reach its maximum height? (Round your answer to two decimal places if necessary.)

   Select an answer meters meters per second seconds seconds per meter 

c) (2 pts) What is the height of the rocket at the time of the launch? (Round your answer to two decimal places if necessary.)

   Select an answer seconds meters meters per second seconds per meter 

Answer 1

Velocity =0 at maximum height ... vel = dh/dt = -9.8t+1200 = 0 @ t= 122.4 seconds.

h(122.4)= 73912 meters a)

t=122.4 seconds b)

h(0) = 320 meters c)