A hot block of solid is dropped in an insulated tank of water at the temperature of

Question:

A hot block of solid is dropped in an insulated tank of water at the temperature of the surroundings. Determine the sign (positive: 1; negative: -1; none: 0) of Q treating
(a) The block as the system.
(b) The water as the system.
(c) The entire tank (with the block and water).