Answer is 13.70% but I do not know how to get to the answer.

An apartment building in your neighborhood is for sale for $140,000. The building has four units, which are rented at $500 per month each. The tenants have long-term leases that expire in 5 years. Maintenance and other expenses for care and upkeep are $8000 annually. A new university is being built in the vicinity and it is expected that the building could be sold for $ 160,000 after 5 years. What is the internal rate of return for this investment