a toy roket is launched upward from the ground, the fomula h(t)=-16t^2+128t gives the height(h) of the object above the ground after seconds(t)

questions:
a. How long will it take the rocket to hit its maximum height? =
b. What is the maximum height? =
c. how long will it take for the rocket to return to the ground? =
d. How far is the rocket from the ground if it already travelled 1 sec? =