Final answer:
The subject of this question is Mathematics, specifically related to interest earnings and fees in a bank account.
Step-by-step explanation:
Based on the given information, the subject of this question is Mathematics. Specifically, it relates to the concept of calculating interest earnings and fees associated with maintaining a minimum balance in a bank account.
The interest rate mentioned in the question is 6%, and there is a minimum balance requirement of $500. Additionally, there is a $15 fee for going under the minimum balance. To calculate the interest earnings, you can use the formula: interest = balance * (interest rate/100). For example, if the average monthly balance is $600, you can calculate the interest earnings as follows: interest = $600 * (6/100) = $36.
To determine if the fee applies, subtract the minimum balance from the average monthly balance. If the result is negative, then the fee applies. In this case, the fee would be $15.