The cost a dog walker for n hours is given by f(n) = 5 + 10n. Which statement is true?

A. For each additional hour of service, the price of the dog walker increases by $15.
B. For each additional hour of service, the price of the dog walker increases by $5.
C. For each additional hour of service, the price of the dog walker increases by $10.
D. For each additional hour of service, the price of the dog walker decreases by $10.