(a) Here$n_{1} = 200\ Hz$.
Number of beats $s^{- 1};m = 4$
$\therefore\ n_{2} = 200 \pm 4 = 204\ or\ 196\ Hz$
On loading fork 2, its frequency decreases. And number of beats $s^{- 1}$ increases to 6. Therefore $m$ is negative.
$n_{2} = 200 - 4 = 196\ Hz$