A car P travelling at 20 ms^-1 sounds its horn at a frequency of 400 Hz. Another car Q is travelling behind the first car in the same direction with…

A car P travelling at $\displaystyle 20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of $\displaystyle 400$ Hz . Another car $\displaystyle Q$ is travelling behind the first car in the same direction with a velocity $\displaystyle 40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car $\displaystyle Q$ is approximately [ Take, velocity of sound $\displaystyle =360 \mathrm{~ms}^{-1}$ ]