Suppose the expression a(b)n models the approximate number of people who visited an aquarium each day since an aquarium opened, where a is the initial number of people who visited, b is the rate of increase in the number of people who visited each day, and n is the number of days since the aquarium opened. If the expression below models the number of visitors of a particular aquarium, what is the correct interpretation of the second factor? 64(1.3)^7