# A whistle of frequency 540 Hz rotates in a horizontal circle of radius 2 m at an angular speed of 15 rad/s. The highest frequency heard by a listener at rest with respect to the center of circle (velocity of sound in air = $330 ms^{-1}$)

$\begin {array} {1 1} (a)\;590 \;Hz & \quad (b)\;594\;Hz \\ (c)\;598\;Hz & \quad (d)\;602\;Hz \end {array}$

(b) 594 Hz