problem 9 please help me solve number 1-4

9. Roberto just took out a loan for $3200 at a 10.8% APR, compounded monthly, to buy a new cello, and he has agreed to make monthly payments of $88 to pay off the loan. He's wondering how much faster he would be able to pay off the loan if he changed his monthly payment to $121. Help Roberto come up with the answer. (4 points: Part I - 1 point, Part II - 1 point; Part Ill - 1 point; Part IV - 1 point) Part I: What Is the periodic interest rate of Roberto's loan? Part II: How long will it take Roberto to pay off the loan by making monthly payments of $88? Part Ill: How long would it take Roberto to pay off the loan by making monthly payments of $121? Part IV: How much faster would Roberto be able to pay off the loan by changing his monthly payment from $88 to $121