Assume that the Tennessee Valley Power Authority (which is exempt from income taxes) issued $100,000 of 30-year maturity, 10 percent coupon, semiannual payment, tax-exempt bonds on January 1, 1997. The bonds were callable after 10 years, or after January 1, 2007, at a price that is 10 percent above the bonds' par value. On January 1, 2007, the Power Authority learns that it can issue $100,000 of new 20-year semiannual payment, 8 percent coupon bonds at par. Costs associated with selling the new issue will amount to $2,000. What is the NPV of the refunding decision