b
\({C_P} - {C_V} = \frac{R}{J}\)

\(\Rightarrow\)  \({C_P} = \frac{R}{J} + {C_V} = \frac{R}{J} + \frac{R}{{J(\gamma  - 1)}}\)

\(\Rightarrow\)  \({C_P} = \frac{R}{J}\left( {\frac{\gamma }{{\gamma  - 1}}} \right) = \frac{R}{J}\left( {\frac{{1.5}}{{1.5 - 1}}} \right) = \frac{{3R}}{J}\)