Answer:
set A: cold water above hot water
Explanation:
The hot water would rise and cold water would sink. This is because hot water is less dense than cold water and would quickly rise and mix with the cold water which would tend to sink. The temperature would change quickly as heat would be transferred from hot to cold till both are in thermal equilibrium.
After a while, in setup B as well, the water would come into thermal equilibrium as water would lose thermal energy to cold water but it will take some time.
