a
(a) Suppose the distance between two fixed points is $d$ then
$t = \frac{d}{v}{\rm{\,\,also \,\,}}v \propto \sqrt T $
$\Rightarrow \frac{{{t_1}}}{{{t_2}}} = \frac{{{v_2}}}{{{v_1}}} = \sqrt {\frac{{{T_2}}}{{{T_1}}}} $
==> $\frac{2}{{{t_2}}} = \sqrt {\frac{{303}}{{283}}} $
$ \Rightarrow $${t_2}= 1.9 \,sec.$