30 year loan is being paid off by amortization, with payments made at the end of each year. The first 5 payments are $0, the next 11 payments are $600 each, and the subsequent 14 payments increase by $100 each year. If the effective interest rate is 10%, Write down an expression for the present value of the loan at t=0. < Write down an expression for the loan balance at the end of 7 years? Write down an expression for the loan balance at the end of 25 years?