A quasi-static cycle of a monoatomic ideal gas contains an isothermal process ($$\boldsymbol{ab}$$), followed by an isochoric process ($$\boldsymbol{bc}$$) and an adiabatic process ($$\boldsymbol{ca}$$) as shown in the figure. The volumes of the gas are $$V_1$$ and $$V_2$$ at $$\boldsymbol{a}$$ and $$\boldsymbol{b}$$, respectively. If the cycle has heat input $$Q_{\text{in}}$$ and output $$Q_{\text{out}}$$, then the efficiency of the cycle is defined as $$\eta=\dfrac{Q_{\text{in}}-Q_{\text{out}}}{Q_{\text{in}}}$$. The correct statement(s) is(are):

[Given: $$\ln 2\approx 0.7$$]