$2.$ A $5[1]$ pressure cooker has an operating pressure of $200[$kPa$].$ Initially, $\backslash (20\backslash \%\backslash )$ of the volume is occupied by liquid and the remainder by vapor. The cooker has a heating unit that supplies heat to the water at a rate of $400[$W$].$ Determine how long it will take for the liquid in the pressure cooker to be depleted $($the cooker contains only saturated vapor at the final state$).$