Question
A Carnot engine (E) is working between two temperatures 473 K and 273 K . In a new system two engines - engine $E_{1}$ works between 473 K to 373 K and engine $\mathrm{E}_{2}$ works between 373 K to 273 K . If $\eta_{12}$, $\eta_{1}$ and $\eta_{2}$ are the efficiencies of the engines $E, E_{1}$ and $\mathrm{E}_{2}$, respectively, then
(1) $\eta_{12}<\eta_{1}+\eta_{2}$ (2) $\eta_{12}=\eta_{1} \eta_{2}$
(3) $\eta_{12}=\eta_{1}+\eta_{2}$ (4) $\eta_{12} \geq \eta_{1}+\eta_{2}$
(1) $\eta_{12}<\eta_{1}+\eta_{2}$ (2) $\eta_{12}=\eta_{1} \eta_{2}$
(3) $\eta_{12}=\eta_{1}+\eta_{2}$ (4) $\eta_{12} \geq \eta_{1}+\eta_{2}$
