Respectively, Cities A, B, and C have 5,000, 10,000, and 12,500 square feet of retail selling space allocated to gift items. Potential customers live 7 minutes from City A, 10 minutes from City B, and 20 minutes from City C. The effect of travel time is 1. According to Huff's law, what percentage of customers will shop in City A for gift items?

a. 9.3
b. 30.5
c. 34.4
d. 37.2