Native Americans boiled water by adding very hot stones to a leak-tight water vessel. What minimum number of \(1.0 \mathrm{~kg}\) stones at \(550^{\circ} \mathrm{C}\) must be added to a vessel holding \(5.0 \mathrm{~kg}\) of \(20^{\circ} \mathrm{C}\) water to bring the water to a boil? Use \(800 \mathrm{~J} / \mathrm{kg} \cdot \mathrm{K}\) for the specific heat of the stones.