1. The problem statement, all variables and given/known data Calculate the maximum possible efficiency of a heat engine that uses surface lake water at 19°C as a source of heat and rejects waste heat to the water 0.100 km below the surface where the temperature is 4.1°C. 2. Relevant equations eta = 1 - Tc / Th 3. The attempt at a solution eta = 1 - 277.1K/292K eta = -.945548 Not sure what I'm doing wrong, am I not supposed to convert to Kelvin??