Honest Joe’s Used RVs offers the following payment options for a used 2015 Freedom 314SO:

1. $49,900 in cash today;

2. $20,000 down payment right now and then $1,200 monthly for the next three years (i.e., 36 payments of $1,200 with the first payment due one month from today).

What effective monthly interest rate is he charging in the second payment option? Note: You can use the IRR function or Goal Seek (or Solver) in Excel to solve this problem.