To start, this is an interest problem, meaning you will have to use I=prt where I is the total interest, p is the principle amount, r is the rate, and time is the amount of time in years. Since you know the principle rate is $1200, the rate is 3.9%, and the time is 8 months, you can plug this into the formula. However, keep in mind that you have to convert 3.9% to a decimal before putting it into the formula and the time must be represented in years. 3.9% represented as a decimal would be 0.039 and 8 months would be represented as 8/12 or 2/3 (since there are 12 months in one year). Now that you have this information, plug the values into the formula: i=(1200)(0.039)(2/3). When simplified, you get your answer as $31.20.