A Plane Is Flying Horizontally at an Altitude of Seven

Multiple Choice

A plane is flying horizontally at an altitude of seven kilometres and a speed of 800 kilometres per hour. At time t = 0 the plane passes over a tracking station on the ground. How fast is the angle of elevation of the plane as measured at the tracking station changing 18 seconds later?

A) increasing at 86 rad/h
B) increasing at 66 rad/h
C) decreasing at 86 rad/h
D) decreasing at 66 rad/h
E) decreasing at 62 rad/h