4. In LACE>MillingtonLACE>, a city of 50,000 people, Mercedes Pedrosa, a realtor, calculated that a family with LACE>MillingtonLACE>’s median family income, $28,000 a year, could afford to buy LACE>MillingtonLACE>’s median-priced $77,000 house. This calculation was based on an 11.2 percent mortgage interest rate and on the realtor’s assumption that a family could only afford to pay up to 25 percent of its income for housing.
Which of the following corrections of a figure appearing in the passage above, if it were the only correction that needed to be made, would yield a new calculation showing that even incomes below the median family income would enable families in Millington to afford Millington’s median-priced house?
(A) LACE>MillingtonLACE>’s total population was 45,000 people.
(B) LACE>MillingtonLACE>’s median annual family income was $27,000.
(C) Millington’s median-priced house cost $80,000.
(D) The rate at which people in Millington had to pay mortgage interest was only 10 percent.（D）
(E) Families in Millington could only afford to pay up to 22 percent of their annual income for housing.
我选的是E,文章不是说25%是假设的吗?为什么选D啊? | 
