Water of mass \(3\text{ kg}\) in a kettle of mass \(1\text{ kg}\) at an initial temperature of \(30^\circ C\) is heated by a heater of power \(2\text{ kW}\). When the lid is open, heat is lost at a constant rate of \(250\text{ Js}^{-1}\). If specific heat capacity of kettle material is half that of water, then time required to raise temperature to \(80^\circ C\) is