Calculate a 30 year amortization schedule in excel for the purchase of an office building. Here are the details:

The building costs $250,000.

You are able to obtain a mortgage loan for 90% of the value.

You must come up with cash for the remaining 10%

The mortgage loan is a fixed rate loan at 6% interest per year using simple interest with a 30/360 formula.

Problem 1 - Calculate the monthly payment of the loan.

Problem 2 - Prepare a detailed amortization schedule month by month for 30 years showing the interest for each month, the remaining balance of the loan for each month of the term.

Problem 3 - Summarize the interest paid per year

Problem 4 - Summarize the principal per year.

Extra Credit Points - 25

For extra credit, calculate the following:

On the 1st month after Year 5 the company pays an additional $10,000 in principal.

On the 1st month after the 10 year the company pays an additional $30,000 in principal.

On the 1st day after the 15th year the company pay an additional $20,000.

Extra Credit Problem 1 - Calculate the net change in total interest paid from the original amortization to the new amortization schedule with the additional principal repayments.

Extra Credit Problem 2 - Calculate the new date when the loan will be finally paid off.

Extra Credit Problem 3 - Calculate the total revised number of payments with the new 3 additional principal payments

I just need the extra credit section done. Can you also show this on a spreadsheet and please list the formulas.

Thanks!