The value of $T_{2}$ if work outputs of both the engines are equal is

Question

A reversible engine operates between temperatures 900 K and T₂ (T₂ < 900 K) and another reversible engine between T₂ and 400 K (T₂ > 400 K) in series. The value of $T_{2}$ if work outputs of both the engines are equal is                    

(a) 600 K                     (b) 625 K        

(c) 650 K                     (d) 675 K