Amoritization Schedule--I have the answers but need to show all work and formulas!

A. Set up an amortization schedule for a $25,000 loan to be repaid in equal installments at the end of each of the next 5 years. The interest rate is 10%.

The answer is: PMT = $6,594.94. Interest = $2,500. Interest = $2,090.51--Show all work/formula

B. How large must each annual payment be if the loan is for $50,000? Assume that the interest rate remains at 10% and that the loan is still paid over 5 years.

The answer is $13, 189.87--show all work and formulas.

C. How large must each payment be if the loan is for $50.000, the interest rate is 10% and the loan is paid off in equal installments at the end of each of the next 10 years? This loan is for the same amount as the loan in part b, but the payments are spread out over twice as many periods. Why are these payments not half as large as the payments on the loan in part b?

The first part of the answer is $8,137.27--show work and formula. The next part requires a written summary-logical answer. Please describe.