Assume you borrow $25,000 student loan from Keystone Bank with 7 years to maturity. To pay back to the loan, you decide to payback Keystone Bank $2500 after 1 year (i.e., at the end of year 1), payback $5000 after 2 year, and payback $7500 after 3 year. After that, you plan to pay back an amount, SW, each year at the end of years 4-7. Assume that the interest rate is 8 percent. How much is the annual payment amount $W that will allow you to pay back student loan throughout the 7-year period?