A liquid solid phase change material $($sodium acetate$)$ of mass $100$ g $.$ Initial temperature of the liquid is at $58\backslash$deg C$.$The transient surface heat transfer rate during the isothermal phase change is given by the following relations :

Q$=$Q$\_0(1-$t$/$pi$)$

Value of Q$\_0$ is $50$ watt.

Assume heat of melting of sodium acetate is deltah$\_$si$=2\mathrm{.}18\backslash$times $10^5$ J$/$Kg

Melting$/$freezing point of sodium acetate is T$\_$ls$=58\backslash$deg C

Assume that the amount of heat released by isothermal phase change will be removed by the transient heat transfer.

Find the elapsed time, torque$\_$in second.