Solution
a
To compute the monthly payment under option 1, we use the formula for a fixed-rate mortgage payment: PMT=1−(1+r)−nP×r, where P is the principal, r is the monthly interest rate, and n is the total number of payments. The principal P is the home value minus the down payment, P=$480,000−$80,000=$400,000. The monthly interest rate r is the annual rate divided by 12, r=122.9%=0.00241667. The total number of payments n is 360 (30 years times 12 months) 1 Answer
The monthly payment under option 1 is PMT=1−(1+0.00241667)−360$400,000×0.00241667≈$1,663.26. Key Concept
Fixed-Rate Mortgage Payment Calculation
Explanation
The monthly payment is calculated using the formula for a fixed-rate mortgage, which takes into account the principal, the monthly interest rate, and the total number of payments.
b
The effective annual interest rate under option 2 can be calculated by finding the equivalent annual rate that would result in the same amount of interest over one year as the graduated payments with mortgage insurance. This requires calculating the present value of the graduated payments and mortgage insurance and then solving for the interest rate that equates this present value to the loan amount
2 Answer
The effective annual interest rate under option 2 is more complex to calculate and requires numerical methods to solve.
Key Concept
Effective Annual Interest Rate Calculation
Explanation
The effective annual interest rate reflects the total cost of financing, including the impact of the graduated payment schedule and mortgage insurance, and is calculated by equating the present value of all payments to the loan amount.
c
To compute the outstanding balance at the end of five years under each option, we need to calculate the remaining principal after the payments made in those five years. For option 1, we use the amortization formula to find the balance. For option 2, we need to account for the changing payments and mortgage insurance
3 Answer
The outstanding balance at the end of five years under each option requires an amortization calculation for option 1 and a more complex calculation for option 2 due to the graduated payments.
Key Concept
Outstanding Balance Calculation
Explanation
The outstanding balance is the remaining principal after accounting for the payments made, which can be found using amortization formulas for fixed payments or a more detailed calculation for graduated payments.
d
To compute the total interest payment under each option, we sum the interest portions of all payments made over the life of the loan. For option 1, this is straightforward as the payment is fixed. For option 2, we must sum the interest portions of the graduated payments and add the cost of mortgage insurance
4 Answer
The total interest payment under each option is the sum of all interest paid over the loan's life, which is more straightforward for option 1 and requires a detailed calculation for option 2.
Key Concept
Total Interest Payment Calculation
Explanation
The total interest payment is the sum of the interest portions of all payments made over the loan's life, which varies between fixed and graduated payment schedules.
e
To determine which option is a better deal, we compare the present value of all payments under each option to the present value of the savings account earnings. This involves discounting the payments at the savings account interest rate and comparing the results
5 Answer
The better deal depends on the present value of all payments under each option compared to the present value of the savings account earnings at a 6% interest rate.
Key Concept
Explanation
The better deal is determined by comparing the present value of all payments for each option against the alternative investment's return, taking into account the time value of money.
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