Problem $5$:

A ball of mass $m=0\mathrm{.}5kg$ is released from a height $h=1\mathrm{.}25$ meters. The ball bounces back to reach a maximum height $h=0\mathrm{.}8$ meters. Find the impulse exerted on the ball by the ground. $($Let $g=10\frac{m}{s^2})$