A certain library assesses fines for overdue books as follows. On the first day that a book is overdue, the total fine is $0.10. For each additional day that the book is overdue, the total fine is increased by $0.30 or doubled, whichever results in a lesser amount. What is the total for a book on the fourth day it is overdue?
i approached it and got 0.90. Somehow this answer is wrong but i am unable to understand the approach for the right answer. somebody please help