Answer:
a. period of the model is 30 seconds
the wheel takes 30 seconds to revolve once
Explanation:
period can be defined as 2pi/b
y = a sin (bx - c) + d
2pi/b
in this case, b would be 1/15pi or pi/15
so
2pi / (pi/15) =
(2pi x 15) / pi = period
30pi/pi = 30
period = 30 seconds