A submarine is moving directly toward a vertical under-water cliff. It fires an ultrasonic pulse and receives the echo 2.0s later. Ten seconds afterwards, it fires a second pulse and receives the echo 1.8s later. The speed of sound in seawater is 1500m/s.
(a) Calculate the distance of the submarine from the cliff at the moment of the first pulse.
(b) Determine the speed at which the submarine is moving toward the cliff.