A steel casting weighing $2kg$ has an initial temperature of $500C$;$40kg$ of water initially at $25C$ is contained in a perfectly insulated steel tank weighing $5kg.$ The casting is immersed in the water and the system is allowed to come to equilibrium. What is its final temperature? Ignore the effects of expansion or contraction, and assume constant specific heats of $4\mathrm{.}18kJ*k{g}^{-1}*K^{-1}$ for water and $0\mathrm{.}50kJ*k{g}^{-1}*K^{-1}$ for steel.