A bat, moving at 6 m/s, is chasing a flying insect. If the bat emits a 42-kHz chirp and receives back an echo at 40.0 kHz, at what speed is the insect moving? (Take the speed of sound in air to be v = 343 m/s.) State your answer to the nearest 0.01m/s.

NOTE: Sign of your answer matters!

Both of the speeds (insect's and bat's ) are measured with respect to the stagnant air.