$200$ kg of nickel at $300$ oC is put in $400$ kg of liquid water at $25$ oC$.$ Assuming the specific heats to be constant $($cnickel$=0\mathrm{.}440$ kJ$.$kg$-1.$K$-1,$ cwater$=4\mathrm{.}180$ kJ$.$kg$-1.$K$-1)$ find the equilibrium temperature in Celsius