Gul buys a 7.6% coupon bond with $1,000 face value and 9.7% yield to maturity. The bond makes semi-annual coupon payments and has 20 years to maturity. The yield to maturity of this bond increases to 10.7% six months later. Calculate Gul's return on investment over the 6-month period. (Intermediate computations should not be rounded. Enter your result as a percentage with two decimal places rounded off. A minus symbol should be used to denote a negative value.) Rate of return %