To calculate the finance charge on the September 10 bill, we need to follow these steps:

1. Determine the average daily balance for the billing period:

• The period under consideration is from August 10 to September 10.
• The balance changes on August 15, August 27, and August 15 (due to purchases and payments).

Step 1: Calculate the daily balances and number of days at each balance level.

• From August 10 to August 14 (5 days): The initial balance is $325.
• From August 15 to August 26 (12 days): After the $79 payment, the balance is $325 - $79 = $246.
• From August 27 to September 10 (15 days): The balance after adding the $151 charge is $246 + $151 = $397.

Step 2: Compute the total balance for the month.

To find the average daily balance, we calculate the total balance across all days:

$\text{Total Balance} = (325 \times 5) + (246 \times 12) + (397 \times 15)$ $\text{Total Balance} = 1625 + 2952 + 5955 = 10532$

Step 3: Calculate the average daily balance.

Now, we divide the total balance by the number of days in the billing period (31 days):

$\text{Average Daily Balance} = \frac{10532}{31} \approx 339.74$

Step 4: Calculate the finance charge.

The interest rate is 1.35% per month. To find the finance charge, multiply the average daily balance by the interest rate:

$\text{Finance Charge} = 339.74 \times 0.0135 = 4.58$

Final Answer:

The finance charge on the September 10 bill is $4.58.

---

Would you like more details on the calculations, or do you have any other questions? Here are some related questions you might find interesting:

1. How would the finance charge change if the interest rate was 1.50% instead of 1.35%?
2. What is the effect of paying the balance off early on the finance charge?
3. How does the timing of purchases and payments impact the finance charge?
4. How would you calculate the finance charge if there were no payment made during the month?
5. What is the difference between average daily balance and previous balance methods for calculating finance charges?

Tip: Always make payments as early as possible within a billing cycle to minimize the interest accrued.