I am having trouble finding a good formula to calculate the initial payment of a Graduated Payment Mortgage. The problem is as follows:

You borrow a GPM of $50,000 with annual payments and 3- year term. The interest rate is 10% and the payment factors from years 1 to 3 are as follows: 50%, 50% and 100%

Questions:

1.What are the annual payments for years 1 to 3?

2.What is remaining balance at the end of year 1?

3.What are interest payment and principal payment for years 1 to 3?