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 18.5°C as a source of heat and rejects waste heat to the water 0.100 km below the surface where the temperature is 4.3°C. 2. Relevant equations e=1-Qc/Qh Q=cm(deltaT) 3. The attempt at a solution I order to calculate the max efficiency I need the heat capacity of water at 18.5°C and 4.3°C. My book only provides 15C and 0C - how am I to solve this problem?