A toy rocket vertically in such a way that t seconds after lift-off, it is

h(t)= -1/2t^2 + 30t feet above ground.

a. How high is the rocket after 40 seconds?

b. What is the average velocity of the rocket over the first 40 seconds of flight (between t

= 0 andt = 40)?

c. What is the (instantaneous) velocity of the rocket at lift-off (t = 0)? What is the velocity

after 40 seconds?