**Hint for process of elimination: **If we read carefully, we notice that the price of a single pair of shoes at the shoe store is $latex a &s=1$. The problem asks for the difference involving the cost of *eight* pairs of shoes at the shoe store. Therefore, the answer must have a term of $latex 8a &s=1$. This eliminates choices A, C, and E.

You can now try to reason through choices B and D. Since you eliminated three choices, you are statistically likely to improve your score by not leaving the answer blank, so you have to choose either B or D.

Read on for a full solution.