A $90$kg athlete performs a drop jump $($jump immediately after landing$)$ from a $0\mathrm{.}5-$meter box. The jump height was $0\mathrm{.}4$ meters.

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What was the$$net$$impulse on the ground?$$Newton$*$Seconds

If the ground contact time is $0\mathrm{.}5$ seconds, what was the average GRF$?$Newtons

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$*$Round answers to nearest whole number $($no decimal$)$