Final answer:
The Btu input rating of an oil-fired furnace with a nozzle rated at 0.85 gpm is 119,000 Btu/hr.
Step-by-step explanation:
The Btu input rating of an oil-fired furnace can be calculated by multiplying the gpm (gallons per minute) rating of the nozzle by the specific heat value of the fuel. In this case, the nozzle is rated at 0.85 gpm. To convert gpm to Btu/hr, we need to multiply the gpm value by 140,000 Btu/hr. Therefore, the Btu input rating of the oil-fired furnace is 119,000 Btu/hr (0.85 gpm × 140,000 Btu/hr).