问一个数学问题，请大家答疑，谢谢。问题如下

A store's Cyber Monday promotion offers electronics at 28 to 70 percent discounted prices. During the promotion, Ali purchases a laptop that is discounted from $355.55 to $165.65. Assume that a 7.5 percent sales tax is included in all prices.

Which of the following approximates the percent discount of Ali's Cyber Monday laptop purchase?

A. 28%

B. 47%

C. 53% 

D. 70%

答案是B 47%. 355.55x = 165.55 x=0.466 

我的问题是为什么不是C 53%. (355.55-165.55)/355.55 = 0.5341