physics about heat

liquid helium has a very low boiling point, 4.2K, as well as a low latent heat
of vaporization, 2.09x10^4 J/kg. If energy is transferred to a container of
liquid helium at the boiling point from an immersed electric heater at a rate
of 6.0 W, how long does it take to boil away 1.5 kg of the liquid?