The figure shows a heat engine (HE) working between two reservoirs. The amount of heat $(Q_2)$ rejected by the heat engine is drawn by a heat pump (HP). The heat pump receives the entire work output $(W)$ of the heat engine. If temperatures, $T_1 >T_3>T_2$, then the relation between the efficiency $(\eta)$ of the heat engine and the coefficient of performance $\text{(COP)}$ of heat pump is
1. $\text{COP}= \eta$
2. $\text{COP}= 1 + \eta$
3. $\text{COP}= \eta^{-1}$
4. $\text{COP}= \eta^{-1} -1$