(a) The maximum velocity for a banked road with friction,
$v^{2} = gr\left( \begin{array}{r}
\frac{\mu + \tan\theta}{1 - \mu\tan\theta} \\
\
\end{array} \right)$
$\Rightarrow v^{2} = 9.8 \times 1000 \times \left( \begin{array}{r}
\frac{0.5 + 1}{1 - 0.5 \times 1} \\
\
\end{array} \right) \Rightarrow v = 172m/s$