Q21. a solid metallic cube of heat capacity s is at temperature 300 k . it is brought in contact with a reservoir at 600 k . if the heat transfer takes place on

Q21. A solid metallic cube of heat capacity S is at temperature 300 K . It is brought in contact with a reservoir at 600 K . If the heat transfer takes place only between the reservoir and the cube, the entropy change of the universe after reaching the thermal equilibrium is (c) 0.27 S (a) 0.69 S (b) 0.54 S (d) 0.19