A boiler generates \(850 \mathrm{~kg}\) of steam per hour at a pressure of \(10 \mathrm{bar}\) and \(50^{\circ} \mathrm{C}\) superheat. It burns \(100 \mathrm{~kg} / \mathrm{h}\) of coal of calorific value \(30 \mathrm{MJ} / \mathrm{kg}\). The feed water temperature is \(30^{\circ} \mathrm{C}\). Calculate

(a) equivalent evaporation from and at \(100^{\circ} \mathrm{C}\) per \(\mathrm{kg}\) of coal, and \((b)\) boiler efficiency. Take \(c_{p s}=2.1 \mathrm{~kJ} / \mathrm{kg} . \mathrm{K}\) and \(c_{p w}=4.187 \mathrm{~kJ} / \mathrm{kg} . \mathrm{K}\).