According to the given data we have the following:
previous balance=$1.30
new balance=$2.05
new balance-previous balance=$2.05-$1.30
new balance-previous balance=$0.75
Therefore, from the day you rent the book until you return it is $0.75.
Therefore if:
5 days overdue___________$0.75
1 day overdue____________x
x= (1 day overdue*$0.75)/5 days overdue
x=$0.15
The charge for one book overdue one day is $0.15