Q21. t'wo carnot engines x and y are operating in series. the engine x receives heat at 1200 k and rejects to a reservoir at a temperature t. the second engine

Q21. T'wo Carnot engines X and Y are operating in series. The engine X receives heat at 1200 K and rejects to a reservoir at a temperature T. The second engine Y receives the heat rejected by X and in turn rejects to a heat reservoir at 300 K . Calculate the temperature T (in Kelvin) for the situation when the efficiency of the engines is same (a) 600 K (b) 750 K (c) 0 (d) 450 K