A quasi-static cycle of a monoatomic ideal gas contains an isothermal process \( (ab) \), followed by an isochoric process \( (bc) \) and an adiabatic process \( (ca) \) as shown in the figure. The volumes of the gas are \( V_{1} \) and \( V_{2} \) at \( a \) and \( b \), respectively. If the cycle has heat input \( Q_{\text{in}} \) and output \( Q_{\text{out}} \), then the efficiency of the cycle is defined as \( \eta = \frac{Q_{\text{in}} - Q_{\text{out}}}{Q_{\text{in}}} \). The correct statement(s) is/are: [Given: \( \ln 2 \approx 0.7 \) ]
