Answer
The required solution is
$2\sec ,69ft$
Work Step by Step
$s\left( t \right)=-16{{t}^{2}}+64t+5$
And compare with
$\begin{align}
& a{{x}^{2}}+bx+c \\
& a=-16 \\
& b=64 \\
& c=5 \\
\end{align}$
Because $a<0$
Thus, the function's maximum value will occur at
$\begin{align}
& t=-\frac{b}{2a}=\frac{-64}{2\times \left( -16 \right)} \\
& t=2 \\
& s\left( 2 \right)=-16{{\left( 2 \right)}^{2}}+64\times 2+5 \\
& =69ft \\
&
\end{align}$
