The lining of an outdoor inground pool needs to be replaced every five years at a cost of $2,500. There is a new type of lining available that would last for 10 years, but costs $6,500. The pool needs new lining now. Your plan is to use the pool for 20 years replacing linnings when needed. If the interest rate is 10% what is the present worth of the cost of 20 years of service for the 10-year lining? what about 5-year lining service?