Dropbox charges $3.10 for first 1/5 of a month for 500 GB storage, plus $0.40 for each additional 1/5 of a month. What would Dropbox charge for a data storage of 500 GB for 8 months ?
Choose the correct choice from the following answers.
A) $ 15.60
B) $ 16.00
C) $ 17.80
D) $ 18.70
E) $ 19.10

Rationale: first 1 / 5 month charge = $ 3.10 rest of the months = 8 - ( 1 / 5 ) = 39 / 5 charge for the rest of the months = 39 * 0.4 = 15.6 total charge = 3.10 + 15.6 = 18.7 answer is d .
Answer: D