A speeding motorcyclist sees traffic jam ahead of him. He slows...

Apparent frequency heard by the observer is given by,
${f}^{'} = {f}_{0}\left(\dfrac{V - {V}_{0}}{V - {V}_{s}}\right)$

Where,

${f}_{0}$ is the original frequency.

$V$ is the velocity of sound.

${V}_{0}$ is the velocity of the observer.

${V}_{s}$ is the velocity of source
${f}^{'} = \left(1392\right)\left(\dfrac{343 - \left(- 10\right)}{343 - \left(- 5\right)}\right) = 1412Hz$