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<span>(t) = 0 gives </span><span>-24t + 60 = 0 </span><span>t = 2.5 </span><span>For this t, the second derivative s"(t) = -24 is negative. And so, s(t) is maximum for t = 2.5. </span><span>Maximum height is S = -12(2.5)^2 + 60(2.5) +8 = 233ft</span>