Mr. Harrington had a new heating system installed in his office. The balance owing to the heating company is $39,000 which includes equipment and installation fees. The heating company has agreed to let him make individual payments on the account whenever hed like, but the final balance must be paid two years (24 months) from now. Starting today, interest will accumulate on the balance at 4.19% compounded monthly. Mr. Harrington will make a payment of $8000 7 months from now and $5000 14 months from now. What is the value of i (the periodic interest rate)?

a. 0.003492 b. 0.001746 c. 2.095000 d. 0.010475