(c) $\frac{T_{2}}{T_{1}} = \left( \frac{P_{2}}{P_{1}} \right)^{\frac{\gamma - 1}{\gamma}\ } \Rightarrow \frac{T_{2}}{T_{1}} = \left( \frac{1}{8} \right)^{\frac{1.5 - 1}{1.5}} = \left( \frac{1}{8} \right)^{\frac{1}{3}} = \frac{1}{2}$
$\Rightarrow T_{2} = \frac{T_{1}}{2} = \frac{300}{2} = 150K$