Of the families in City X in 1994, 40 percent owned a personal computer. The number of families in City X owning a computer in 1998 was 30 percent greater than it was in 1994, and the total number of families in City X was 4 percent greater in 1998 than it was in 1994. What percent of the families in City X owned a personal computer in 1998?

A. 50%

B. 52%

C. 56%

D. 70%

E. 74%

答案是A, 可我算出来是54%(0.4*1.3*1.04).

请问怎么得出A的?

1994年的,有电脑的0.4a,总人数a

1998年的,有电脑的1.3X0.4a,总人数1.04a

除一下,正好是50%