c. A building owner has the plan to retrofit the air conditioning (AC) system. There are three options to carry out the project including, i) Replace the entire old air conditioning system with a more efficient one. The old AC system has an efficiency of 70%, while a new AC system can have an efficiency of 85%. The cost for this replacement is $10000. ii) Replace only the chiller of the old AC system, which can increase the efficiency of the AC system to 75%. This will cost $3000. iii) Do nothing and replace neither the AC system nor the chiller. The AC system consumes 6000 kWh electricity at 1$/kWh. An annual maintenance fee of $200 is needed and other operation costs of the AC system are ignorable. Assume that the life time of the retrofit project is 10 years and the discount rate is 5%. By the end of the life time, the residual value of the new AC system is $2000 only, while zero for the old AC system (with or without chiller replacement). Determine the best economical option for the building owner using life cycle cost (LCC) analysis method. (8 marks)