20. Two blocks of steel, the first of mass 1 kg and the second of mass 2 kg , are in thermal equilibrium with a third block of aluminum of mass 2 kg that has a temperature of 400 K . What are the respective temperatures of the first and second steel blocks?
(A) 400 K and 200 K
(B) 200 K and 400 K
(C) 400 K and 400 K
(D) 800 K and 400 K