It is desired to cool iron parts from 500�F to 100�F by dropping them into water that is initially at 65�F. As?

It is desired to cool iron parts from 500�F to 100�F by dropping them into water that is initially at 65�F. Assuming that all the heat from the iron is transferred to the water and that none of the water evaporates, how many kilograms of water are needed per kilogram of iron?