(4) We have 1000 L of crude oil as input. After refining for 1 h, we get Output = 90% of 1000= 900 L Profit = 7 900 x 30 = ₹ 27000 Further refining for 1/2 h, we get Output = 90% of 900 = 8100 L Profit = 7 8100 x 50 = ₹ 40500 Hence, maximum profit = ₹ 40500