An aluminium vessel of mass `0.5kg` contains `0.2kg` of water at `20^(@)C` A block of iron of mass `0.2kg at 100^(@)C` is gently put into the water .Find the equilibrium temperature of the mixture,Specific beat capactities of aluminium , iron and water are `910 J kg^(-1)K^(-1) 470J kg^(-1)K^(-1) and 420J kg^(-1)K^(-1)` respectively