Janet has three times as many dimes as nickels and twice as many quarters as nickels. If she has $5.10 in all, how many nickels, dimes, and quarters does she have? If n represents the number of nickels Janet has, which of the following equations could be used to solve the problem?
a). 5n + 10n + 25n = 510
b). n + 3n + 2n = 510
c). 5n + 30n + 50n = 510