The $2-$kg block is subjected to a force having a constant

direction and a magnitude $F=(\frac{300}{s^2})$ Newton, where $s$ is

in meters. When $s=4m,$ the block is moving to the left

with a speed of $8\frac{m}{s}.$ Determine its speed when $s=12m.$

The coefficient of kinetic friction between the block and the

ground is ${}_k=0\mathrm{.}25.$