To determine the amount required to pay the entire balance of the invoice, we need to break down the terms and the timeline of the payment. Here's the step-by-step process:

Step 1: Understanding the Terms

• 4/15: A 4% discount is available if paid within 15 days from the invoice date.
• 3/25: A 3% discount is available if paid within 25 days from the invoice date.
• n/50: The net amount (no discount) is due within 50 days.
• 1.25% per month: A late penalty of 1.25% per month is applied after 50 days.

Step 2: Timeline of the Payment

• The invoice date is September 16.
• The payment date is November 13.

Now, let's compute how many days after the invoice the payment is made:

• From September 16 to November 13 is 58 days.

Step 3: Analyzing the Payment Window

• 4/15 discount: The payment should have been made within 15 days, by October 1. This is missed.
• 3/25 discount: The payment should have been made within 25 days, by October 11. This is also missed.
• n/50: The net payment should have been made within 50 days, by November 5. This deadline is also missed.

Since the payment is made on November 13, 58 days after the invoice date, it is 8 days past due, meaning the full amount is subject to a late penalty.

Step 4: Applying the Late Penalty

The late penalty is 1.25% per month. We need to apply this penalty for the 8 days overdue, which corresponds to part of a month.

1. Number of months overdue:
   $\frac{8}{30} \approx 0.267$ months.

2. Late penalty calculation:

   • The late penalty for 1.25% per month over 0.267 months on the full amount is: $\text{Late penalty} = 14,000 \times 1.25\% \times 0.267 = 14,000 \times 0.0125 \times 0.267 = 46.79$

Step 5: Final Payment Amount

Since no discounts were applied, the full amount of $14,000 is owed plus the late penalty of $46.79.

Thus, the total payment required on November 13 is: $\text{Total payment} = 14,000 + 46.79 = 14,046.79$

Final Answer:

The total payment amount required on November 13 is $14,046.79.

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Would you like a breakdown of any specific step? Here are five related questions you might consider:

1. What happens if the invoice is paid within 15 days?
2. How would the late fee change if the payment was made on November 20 instead of November 13?
3. How does the penalty rate compare to typical credit card interest rates?
4. If a discount had been applied, how would the final amount change?
5. What if the penalty was compounded monthly?

Tip: Always take advantage of early payment discounts to reduce the total payable amount, if cash flow allows!