Problem Solving 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 either increased by $0.30 or doubled, whichever results is in the lesser amount. What is the total fine for a book on the fourth day it is overdue? A $0.60 B $0.70 C $0.80 D $0.90 E $1.00 为什么是B？ 高亮色的那句怎么解释啊？ | 
