A sound wave travels with a velocity of $300\: ms^{-1}$ through a gas. 9 beats are produced in 3 sec when two waves pass through it simultaneously. If one of the waves has 2 m wavelength, the wavelength of the other wave is :

Question

$\begin {array} {1 1} (1)\;1.98 \: m & \quad (2)\;2.04\: m \\ (3)\;2.00\: m & \quad (4)\;1.99\: m \end {array}$