Okay, let's find the unit rate of cost. To find that for store A, we divide 7.26 by 3, which gets us 2.42. For store B, we need to look for the first intersection. We find that at (20, 50). Let's divide 50 by 20. That gets us 2.50. Let's multiply 2.42 and 2.50 by 16. That gets us 38.72 for store A and 40 for store B. Let's subtract 38.72 from 40. That gets us 1.28. That means store A costs $1.28 less than store B. That makes our answer A.
