I need help with 18, 19, and 20

018 10.0 points A steam engine ( assume a Carnot engine ) has an efficiency of 79.1% If the waste heat has a temperature of 50.1'C. what is the temperature of the boiler? Answer in units of C. 019 (part 1 of 2) 10.0 points A Carnot engine has a power output of 68 kW. The engine operates between two reservoirs at 28"C and 355'C. How much thermal energy is absorbed each hour? Answer in units of .J. 020 (part 2 of 2) 10.0 points How much thermal energy is lost per hour? Answer in units of J