4. You are eager to improve the efficiency of the water heating in example 3 above. You measure the steady-state efficiency (SSE) of the boilers, one gas-fired and the other oil-fired, and obtain the following results: 4a - What is the SSE of the gas-fired boiler? 4b - What is the SSE of the oil-fired boiler? 4c - A trusted burner mechanic tells you that the best possible tuneup for the burner on your boiler will bring the O2 reading down to 4% and the gross stack temperature down to 325F for both oil and gas. What is the best possible SSE when burning gas under those circumstances (assume the boiler room air temperature is 75F )? 4d - When burning oil