An Olympic swimming pool is initially at 20 C. It is heated by flowing pool water over a hot surface with an area of 100 m^2. The hot surface is heated by hot water on the other side that has a constant temperature of 50 C. The overall heat transfer coefficient kh of the hot surface is 2000 W/(m^2.K).

The pool itself has a water volume of 3000 m^3. The water has a density of 1000 kg/m^3 and a heat capacity of 4180 J/kg.K Question: How long does it take to heat the pool from 20 C to 25 C?