A Plane Flying Horizontally at an Altitude of 1 Kilometre

Multiple Choice

A plane flying horizontally at an altitude of 1 kilometre and a speed of 500 kilometres per hour passes directly over a radar station. Find the rate at which the distance from the plane to the station is increasing at the instant when the plane is 2 kilometres away from the station.

A) 350 kilometres per hour
B) 462 kilometres per hour
C) 402 kilometres per hour
D) 433 kilometres per hour
E) 382 kilometres per hour