TS EAMCET Medical 2015 Paper

Two trains A and B are approaching a platform from opposite directions. The siren in the station is making a sound at a frequency 4 kHz. The passengers in the trains A and B hear it as sound with frequencies 4.5 kHz and 5 kHz respectively. Then the velocitiesof the trains A and B are,
(velocity of sound in air = 340 m/s)