A boiler produces 9000 kg of steam while 1 tonne of coal is burnt. The steam is produced at 10 bar (h_{f} = 762.6 kJ/kg, h_{fg} = 2013.6 kJ/kg) from feed water at 15 °C (take h_{fw} ≈ 4.187 × t), with dryness fraction 0.9. The calorific value of the coal is 32 000 kJ/kg. Determine the boiler efficiency (answer in %).