Based on a 20-year mortgage requiring monthly payments at prime rate minus 2.5%, and 30% down payment for a 40 square meters apartment in Hong Kong, the year in which average home ownership was least affordable is:

Year	Median Household Income per month (HK$)	Price per sq. meter. (HK$)	Prime Rate (%)
20x1	16,000	36,050	7.5
20x2	17,000	38,910	7.5
20x3	17,500	43,184	7.5
20x4	18,000	58,655	7.5
20x5	17,500	55,000	7.5

Select one:

a. 20x1

b. 20x4

c. 20x3

d. 20x2

e. 20x5