The steam requirements of a manufacturing facility are being met by a boiler whose rated heat input is 5.5 x 106 Btu/h. The combustion efficiency of the boiler is measured to be 0.65. After tuning up the boiler, the combustion efficiency rises to 0.75. The boiler operates 4000 hours a year intermittently. Take the unit cost of energy to be $4.35/106 Btu. Assuming the same heat output for before and after the tunning:________.