The following data is available from a boiler trial :

Duration \(=1\) hour, steam generated \(=36000 \mathrm{~kg}\), steam pressure \(=12.5 \mathrm{bar}\), steam temperature \(=250^{\circ} \mathrm{C}\), temperature of water entering the economiser \(=16^{\circ} \mathrm{C}\), temperature of water leaving the economiser \(=75^{\circ} \mathrm{C}\), oil burned \(=3500 \mathrm{~kg}\), C.V. of oil \(=39500 \mathrm{~kJ} / \mathrm{kg}\), specific heat of steam \(=2.1 \mathrm{~kJ} / \mathrm{kg}\).K. Calculate 

(a) equivalent evaporation per \(\mathrm{kg}\) of fuel, 

(b) thermal efficiency, and

(c) percentage of heat energy of flue gases utilized by the economiser.