\(T V^{\gamma-1}=K\)
\(\log T+(\gamma-1) \log V=0\)
\(\log T=-(\gamma-1) \log V\)
\(y=-(\gamma-1) x\)
\(\frac{y}{x}=-(\gamma-1)=\text { slope }=\frac{2-4}{4-1}\)
\(\Rightarrow-(\gamma-1)=-\frac{2}{3}\)
\(\gamma=\frac{5}{3}\)
\(\therefore \text { Monoatomic.}\)