Compute the correct solution of the given question

Question- It is proposed that the exhaust gases from a diesel engine generating electricity is used to preheat air. The mass flow rate of exhaust available from the diesel engine is 110kg/h at a temperature of 325c. The air is at 25c ambient temperature and it has to be heated to 80c at a mass flow rate of 120kg/h. there are a number of double pipe heat exchangers that are 2m long. the exchanger consist of an inner pipe if 3in type K copper tubing jacketed with 4 in type K copper tube. The air should be directed through the inner pipe. Assume counter flow arrangement neglect the tube wall resistance to heat transfer. Assume that the diesel exhaust had the same properties as CO2 gas.

Part A- Determine how many double pipe exchangers are required.

Part B- Calculate the heat transfer coefficient for the exchanger(s).

I need expert's assistance to determine the heat transfer coefficient for the exchanger.