which formula i should use help

Task 1 Using Excel's built in financial functions create a model for calculating your loan's interest rate. You have a $13000 loan that can be paid off with 12 annual payments of $1250 each if you make the first payment one year from now. What is the interest rate on the loan? What if the loan involves a $2000 additional final payment? Add spinners to you model for loan amount from 10000 up to 20000 and for per period payments up to $2000. Protect your model