A $2.0\ \text{kW}$ stove passes $60\%$ of its heat to a pan of $0.50\ \text{kg}$ of water already boiling at $100\ ^\circ\text{C}$. How long until all the water has boiled away? (Latent heat of vaporisation $2.26 \times 10^{6}\ \text{J/kg}$.)