Please make the final answer for A and B bold. Thank you!!

A car dealer is selling a new Dodge Charger for $42,000 cash, or monthly payments of $840 for 72 months (6 years). What monthly interest rate is the dealer charging? To solve this, we use the Present Value Annuity formula, which is: A=iR[1(1+i)n] A is the total amount, R is the monthly payment, and i is the monthly interest rate. Replacing i with x and solving for x gives this: (1+x)n(RAx1)+1=0 Substituting the values for n,A and R gives: (1+x)72(50x1)+1=0 Use the Newton-Raphson method in Excel to: a) solve for x, the monthly interest rate b) calculate how much total interest you paid for the life of the loan (6 years)