Please show work on excel so I can follow the steps!

You work for a mortgage lender. Your competitor is offering a 20-year FRM for $675,500 at 3.1% interest, along with an optional second mortgage for $124,500 at 13% interest. 1. What mortgage payments is your competitor receiving on these two loans? 2. If you want to be competitive with them, what mortgage payment and interest rate should you offer on a $800,000 mortgage? A borrower takes you up on your offer. Five years into the $800,000 mortgage, they decide to refinance because interest rates have decreased by 50 basis points. 3. What is the loan balance that they must repay on the old loan? 4. What is the mortgage payment on the new loan? 5. If your discount rate is 7.5%, how much should you charge in upfront loan origination fees to make up for the losses you will incur in lower mortgage payments? The borrower takes you up on this new offer, including the loan origination fees. But they have to move and sell the house five years later. 6. Was refinancing a good investment for them? How do you quantify this assessment