An investor has 10 bonds paying a 4% semiannual coupon, maturing in 10 years and priced at a yield to maturity of 5%. The duration of these bonds is 8.25 years. The investor also has 8 bonds maturing in 5 years that are priced at par and pay a coupon of 4.5%. The duration of these bonds is 4.50 years. If interest rates increase 1 percentage point for all maturities, what is the approximate change in price of the investor's portfolio?

A.) 7.00%

B.) 6.51%

C.) 6.58%

D.) 6.23%

E.) 6.38%