15. Suppose that a bond promises to pay its holder $100 a year forever. If the price of the bond increases from $1,000 to $1,250, then the interest rate on the bond (A)falls from 10 percent to 8 percent. (B) rises from 8 percent to 10 percent. (C)does not change because it is not affected by the price of the bond. (D)falls from 10 percent to 6 percent.