Suppose that you have a $400,000 commercial mortgage with a 6.3% APR and a 25 year amortization period. Further, suppose that the mortgage has a 5 year balloon.

How much of the 48th monthly payment is interest and how much is principal? What is the amount of the balloon payment excluding the final monthly payment?

To calculate the amount of interest and principal for the 48th monthly payment, and to determine the balloon payment excluding the final monthly payment, you can use the formulas for an amortizing loan.

First, let's calculate the monthly payment using the amortization formula:

P = L[c(1 + c)^n]/[(1 + c)^n - 1]

Where:
P = Monthly payment
L = Loan amount
c = Monthly interest rate
n = Total number of payments

Given:
L = $400,000
APR = 6.3% = 0.063
Amortization period = 25 years (25 * 12 = 300 months)
Balloon period = 5 years (5 * 12 = 60 months)

1. Calculate the monthly interest rate:
c = APR / 12
c = 0.063 / 12
c = 0.00525

2. Calculate the monthly payment:
P = $400,000 * [0.00525(1 + 0.00525)^300] / [(1 + 0.00525)^300 - 1]
= $2,482.08

Now, let's calculate the amount of interest and principal for the 48th monthly payment:

3. Calculate the interest for the 48th monthly payment:
Interest = Loan amount * Monthly interest rate
Interest = $400,000 * 0.00525
Interest = $2,100

4. Calculate the principal for the 48th monthly payment:
Principal = Monthly payment - Interest
Principal = $2,482.08 - $2,100
Principal = $382.08

Therefore, for the 48th monthly payment, the amount of interest is $2,100 and the amount of principal is $382.08.

Now, let's calculate the balloon payment excluding the final monthly payment:

5. Calculate the remaining loan balance after the 55th payment (48 regular payments + 7 balloon payments):
Remaining balance = Loan amount * [(1 + c)^n - (1 + c)^m] / [(1 + c)^n - 1]

Where:
m = Number of payments made before the balloon payment
n = Total number of payments

Given:
m = 48 (48 regular payments before the balloon payment)
n = 60 (Total number of payments including the balloon payment)

Remaining balance = $400,000 * [(1 + 0.00525)^60 - (1 + 0.00525)^48] / [(1 + 0.00525)^60 - 1]
= $303,047.60

Therefore, the balloon payment excluding the final monthly payment is $303,047.60.

Note: The final monthly payment will consist of the remaining balance after 299 payments.