A 1000 par value 10-year bond is purchased on its issue date. The bond pays semi-annual coupons at an 8% annual coupon rate. Based on the purchase price, the bond's yield to maturity is 6% convertible semi-annually. The bond is sold 4 years later, having provided a yield of 6.4% convertible semi-annually during those 4 years. What is the difference between the bond's purchase price and its sale price