The maintenance cost is incurred at the end of the year

Two machines are being considered for the same task. Machine A costs $18,000 new and is estimated to last 6 years. The cost to replace machine A after 6 years will be $23,000. Machine A will cost $1,200 per year to operate/maintain and it will have a trade-in (salvage) value of $1,500. Machine B costs $38,000 to buy, will last 12 years and will have a trade in value of $2,000. The cost of operation and maintenance for machine B is $700 per year. Compare the two machines on a present worth basis and state which machine will be cheaper and by how much. Include a cash flow diagram for each option. Assume that all interest rates are 8% per year compounded monthly