A milkman buys milk at a price of Rs. 35 per litre and sells at a price of Rs. 40 per litre. He uses faulty measurement cups for measuring the milk, which measures 220 ml instead of 250 ml, 450 ml instead of 500 ml and 920 ml instead of 1 litre. If a customer buys 2.75 litres of milk, find the profit % earned by the milkman.