4) Solve the following problems involving annuity functions and unknown number of payments Able owes $20,000 to Baker at 8% interest. Able agrees to pay Baker $2000 every year starting in one year for as long as required to pay back the debt, decreasing the last payment amount as required. Find the number of payments and the amount of the last payment. Charlie saves $2000 every January 1 starting in 2017. If she earns 5% interest, when does her accumulated value first exceed $20,000 a) b)