The cheetah can reach a top speed o$1$

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$$While chasing its prey in a short sprint, a cheetah starts from rest and runs $50$m in a straight line, reaching a final speed of $86$ km$/$h$.$

$($a$)$Determine the cheetah's average acceleration during the short sprint. $($in m$/$s$^2)$

$($b$)$Find its displacement at t $=3\mathrm{.}1$ s$.($Assume the cheetah maintains a constant acceleration throughout the sprint.$)$ put the answer in meters