An engine operates by taking n moles of an ideal gas through the cycle $ABCDA$ shown in figure. The thermal efficiency of the engine is : (Take Cv=1.5 R, where R is gas constant)

Question

$\begin{array}{1 1}(1)\; 0.24\\ (2)\; 0.15\\ (3)\; 0.32\\ (4)\; 0.08 \end{array}$