NEET Exam Model Paper 2

A train has just completed a U-curve in a track which is a semicircle, the engine is at the forward end of the semi circular part of the track while the last carriage is at the rear end of the semicircular track, the driver blows a whistle of frequency 200 Hz. velocity of sound is 340 m/sec. Then the apparant frequency as observed by a passenger in the middle of a train when the speed of the train is 30 m/sec is