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40 sec

42 sec

45 sec

48 sec

A. 40 sec

$\mathit{F}\mathit{o}\mathit{r}\mathit{m}\mathit{u}\mathit{l}\mathit{a}\mathbf{}\mathit{f}\mathit{o}\mathit{r}\mathbf{}\mathit{c}\mathit{o}\mathit{n}\mathit{v}\mathit{e}\mathit{r}\mathit{t}\mathit{i}\mathit{n}\mathit{g}\mathbf{}\mathit{f}\mathit{r}\mathit{o}\mathit{m}\mathbf{}\mathit{k}\mathit{m}\mathbf{/}\mathit{h}\mathit{r}\mathbf{}\mathit{t}\mathit{o}\mathbf{}\mathit{m}\mathbf{/}\mathit{s}\mathbf{:}Xkm/hr=\left(X\times \frac{5}{18}\right)m/s.\phantom{\rule{0ex}{0ex}}Therefore,Speed=\left(45x\frac{5}{18}\right)m/sec=\frac{25}{2}m/sec.\phantom{\rule{0ex}{0ex}}Totaldis\mathrm{tan}cetobecovered=(360+140)m=500m.\phantom{\rule{0ex}{0ex}}\mathit{F}\mathit{o}\mathit{r}\mathit{m}\mathit{u}\mathit{l}\mathit{a}\mathbf{}\mathit{f}\mathit{o}\mathit{r}\mathbf{}\mathit{f}\mathit{i}\mathit{n}\mathit{d}\mathit{i}\mathit{n}\mathit{g}\mathbf{}\mathit{T}\mathit{i}\mathit{m}\mathit{e}\mathbf{}=\left(\frac{Dis\mathrm{tan}ce}{Speed}\right)\phantom{\rule{0ex}{0ex}}\therefore Requiredtime=\left(\frac{500x2}{25}\right)sec=40sec.$