Any help would be greatly appreciated. This is all the information given.

A counterflow concentric tube heat exchanger used for engine cooling in a very hot enviroment has been in servive for an extended period of time. The heat transfer surface area of the exchanger is 5m^2 and the design valueof the overall convection coefficient is 33W/m^2k. During a test run, engine oil flowing at 0.1kg/s is cooloed from 110°C to 66°C by water supplied at a temperature of 25°C and a flow rate of 0.2kg/s

a) Calculate the operating convection coefficient
If the ambient temperature is 50°C give a possible reason for the
discrepancy