Peter is making payments on his mortgage. Every month, his payment is different. Each payment consists of a fixed amount, that is credited toward the prinicpal, and an additional amount for the interest that is due on the balance that is due as of the last payment. As the loan matures, Peter's payments become smaller. What type of payment plan does Peter have? A fully amortized loan A term loan A partially amortized loan A straight-line amortized loan