$[5]$ A combination of $0\mathrm{.}250$ kg of water at $20\mathrm{.}0C,0\mathrm{.}400kg$ of aluminum at $50C,$ and $0\mathrm{.}100$ kg of copper at $100C$ is mixed in an insulated container and allowed to come to thermal equilibrium. Ignore any energy transfer to or from the container. What is the final temperature of the mixture?