To calculate the average daily balance and answer each part of the question, we need to consider the daily balances and the number of days each balance is held. Let's go through the problem step by step.

---

Part 1: Find the average daily balance for the billing period.

1. March 1–March 4 (4 days): The balance is the previous balance, $6,230.00.

2. March 5–March 6 (2 days): After a payment of $300, the balance is reduced to $6,230.00 - $300.00 = $5,930.00.

3. March 7–March 11 (5 days): A restaurant charge of $60 is added, making the balance $5,930.00 + $60.00 = $5,990.00.

4. March 12–March 20 (9 days): A grocery charge of $90 is added, making the balance $5,990.00 + $90.00 = $6,080.00.

5. March 21–March 31 (11 days): A car repair charge of $270 is added, making the balance $6,080.00 + $270.00 = $6,350.00.

Now, let's calculate the weighted balance (balance * days held):

$\text{Weighted Balance} = (6230.00 \times 4) + (5930.00 \times 2) + (5990.00 \times 5) + (6080.00 \times 9) + (6350.00 \times 11)$

$\text{Weighted Balance} = 24,920 + 11,860 + 29,950 + 54,720 + 69,850 = 191,300$

The total number of days in the billing period is 31.

$\text{Average Daily Balance} = \frac{191,300}{31} = 6,174.19$

Answer for Part 1:

$\boxed{6,174.19}$

---

Part 2: Find the interest to be paid on April 1.

The monthly interest rate is 2.52%. To find the interest, we use the formula:

$\text{Interest} = \text{Average Daily Balance} \times \frac{\text{Interest Rate}}{100}$

Substitute the values:

$\text{Interest} = 6,174.19 \times \frac{2.52}{100} = 6,174.19 \times 0.0252 = 155.59$

Answer for Part 2:

$\boxed{155.59}$

---

Part 3: Find the balance due on April 1.

To find the balance due, add the interest to the balance at the end of the billing period (March 31 balance of $6,350.00):

$\text{Balance Due} = 6,350.00 + 155.59 = 6,505.59$

Answer for Part 3:

$\boxed{6,505.59}$

---

Part 4: Find the minimum monthly payment due by April 9.

The minimum monthly payment is determined as follows:

• If the balance due is less than $360, the minimum payment is $10.
• If the balance due is more than $360, the minimum payment is 1/36 of the balance due, rounded up to the nearest dollar.

Since the balance due is $6,505.59:

$\text{Minimum Payment} = \frac{6,505.59}{36} = 180.71$

Rounding up to the nearest dollar:

$\text{Minimum Payment} = 181$

Answer for Part 4:

$\boxed{181}$

---

Summary of Answers:

• Part 1: $6,174.19 (Average Daily Balance)
• Part 2: $155.59 (Interest to be paid)
• Part 3: $6,505.59 (Balance due)
• Part 4: $181 (Minimum monthly payment)

---

Would you like more details or clarifications? Here are five related questions:

1. How does the average daily balance method compare to other methods like adjusted balance or previous balance methods?
2. What would happen to the interest if there were more charges or payments throughout the month?
3. How would the minimum payment change if the interest rate increased?
4. How does compounding interest differ in credit card calculations versus loans?
5. Can paying more than the minimum payment affect the overall interest paid?

Tip: Always aim to pay more than the minimum payment to reduce interest and pay off the balance faster.