To determine on which day Isabelle gets charged an overdraft fee, we need to calculate her balance at the end of each day after applying the debits (purchases) and credits (deposits). She starts with a balance of $84.00.
Sunday:
- Starting Balance: $84.00
Monday:
- Debit: $22.35
- New Balance: $84.00 - $22.35 = $61.65
Tuesday:
- Debit: $47.60
- Credit: $10.29
- New Balance: $61.65 - $47.60 + $10.29 = $24.34
Wednesday:
- Debit: $15.44
- New Balance: $24.34 - $15.44 = $8.90
Thursday:
- Debit: $11.25
- New Balance: $8.90 - $11.25 = -$2.35
Since the balance is negative, this indicates that Isabelle is charged an overdraft fee on Thursday.
Friday:
- Debit: $9.78
- Credit: $22.69
- New Balance: -$2.35 - $9.78 + $22.69 = $10.56
Isabelle's balance is positive on Friday, so she is not charged an overdraft fee.
Saturday:
- Debit: $30.54
- Credit: $18.86
- New Balance: $10.56 - $30.54 + $18.86 = -$1.12
Again, the balance is negative on Saturday, which indicates that she is charged an overdraft fee.
To summarize:
- Overdraft fee on Thursday: Yes
- Overdraft fee on Friday: No
- Overdraft fee on Saturday: Yes
The correct answer is b. I and III.