Answer: I. Thursday and III. Saturday
Explanation: To say that Isabelle has $84.00 in her account means that she has her own cash held in a bank. This means that Isabelle has a debit account and is likely using a debit card to for her deposits and purchases. A debit card is used to take out cash from her account, and not a line of credit. This means that the cash for every purchase she makes is withdrawn from her account which then debits, or decreases her balance. On the other hand every deposit into her account, increases the balance which is credited to her account.
The changes made throughout the week affected her account in the following way:
Day Debit(-) Credit (+) Balance
Openin bal: 84.00
Monday -22.35 61.65
Tuesday -47.60 +10.29 24.34
Wednesday -15.44 8.90
Thursday -11.25 -2.35
Friday -9.78 +22.69 10.56
Saturday -30.54 +18.86 -1.12
∴closing bal: = -1.12
From this it shows that Isabelle is charged an overdraft fee on Thursday (I) and Saturday (III) as she spent more than what she had in her account on those days.