A Jet Plane in Straight Horizontal Flight Passes Over Your $\degree$

A jet plane in straight horizontal flight passes over your head.When it is directly above you, the sound seems to come from a point behind the plane in a direction 30 $\degree$ from the vertical.The speed of the plane is:

A) the same as the speed of sound
B) half the speed of sound
C) three-fifths the speed of sound
D) 0.866 times the speed of sound
E) twice the speed of sound