Andy is flying an airplane that is 12,000 feet in the air.

D   21.80°

Step-by-step explanation:

Let x = measure of the angle

Tan x = 12000/30000 = .4

Arctan .4 = 21.80°

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50