A shell and tube heat exchanger is used to cool 5000 kg/hr of water from 90C to 40C using cooling water from a river that enters the heat exchanger at 25C and leaves at 30C. The overall heat transfer coefficient is 200 W/(m²*K), and the heat exchanger has a surface area of 50 m². Calculate the heat transfer rate and the LMTD of the heat exchanger, and the number of tubes needed.

(The tubes have an outer diameter of 25 mm and a length of 3 m)