A rock bed consists of 6000 kg granite and is at 70C. A small house with lumped mass of 12000 kg wood and 1000 kg iron is at 15C. They are now brought to a uniform final temperature with no external heat transfer.
a. For a reversible process, find the final temperature and the work done in the process.
b. If they are connected thermally by circulating water between the rock bed and the house, find the final temperature and the irreversibility of the process, assuming that surroundings are at 15C.