Room air conditioners are often rated with a non-SI quality measure called the energy efficiency rating, EER, expressed in mixed units. According to the source, what does EER measure?

1. The source introduces EER as a consumer-facing rating that mixes non-SI and SI units rather than following the pure COP definitions used elsewhere. 2. It defines EER as British thermal units of heating or cooling per hour divided by the power input in watts. 3. Option A inverts this ratio, putting watts in the numerator instead of the denominator. 4. EER is not simply the Carnot efficiency restated as a percentage, and it does not divide joules by kelvins, since it explicitly mixes Btu-per-hour with watts, ruling out options B and C. _Source: OpenStax College Physics (CC BY 4.0), Ch 15 "Thermodynamics", section 15.5 Applications of Thermodynamics: Heat Pumps and Refrigerators_