一道数学题，求解释~~

寻沫访华

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 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.$080
D.$0.90
E.$1.00

此题选B是为什么呀，题目和解题方法，求解释~~

七百年后

题目说图书馆对过期不还书进行罚款，规则是过期的第一天罚0.10，之后每多一天，多罚0.30或者将累计罚金翻倍，取结果少的方法。要求4天罚多少钱
第一天0.10
第二天  翻倍是0.2，而增加0.3是0.4 取少的0.2
第三天 翻倍是0.4 增加0.3是0.5 取0.4
第四天 翻倍是0.8 增加0.3是0.7 取0.7
SO, B

lpbird

我以为必须用一种方式

永远爱koma62

解释的好啊~~~~~~~~~