Piece of iron immersed in water

A piece of iron of mass $0.25\mathrm{kg}$ at a temperature of $200{}^{\circ }\mathrm{C}$ is immersed in $1.0\mathrm{kg}$ of water at $20{}^{\circ }\mathrm{C}$, in an insulated container of negligible heat capacity. Compute the equilibrium temperature ($c_{\mathrm{Fe}}=450J/(\mathrm{kg}\cdot \mathrm{K})$, $c_a=4186J/(\mathrm{kg}\cdot \mathrm{K})$).