An object, moving with a speed of $6.25 \mathrm{~m}/\mathrm{s}$, is decelerated at a rate given by :
$$\frac{\mathrm{dv}}{\mathrm{dt}} = -2.5\sqrt{\mathrm{v}}$$
where $v$ is the instantaneous speed. The time taken by the object, to come to rest, would be:\\
(1) 2 s\\
(2) 4 s\\
(3) 8 s\\
(4) 1 s