Math help ferris wheel

Question

The height of a person above the ground on a Ferris wheel is given by the function h(t)=9 sin {pi/20 (t- pi/2))+ 12 where h(t) is the height in meters of person t seconds after getting on
a) how long does it take the Ferris wheel to make one complete revolution
b)what is the height of the ferris wheel if the riders get on at 15s

Answer 1

h= 9sin((pi/20)(t - pi/2))+12

pi/20 = 2pi/period

period = 40

at t =15

h = 9sin(pi/20)(15-pi/2)) +12

= 9sin(3pi/4 -2pi/2) +12

= 9sin(pi/2) +12

= 9+12

= 21 feet

after 15 seconds= max height = top of the ferris wheel ride