Final answer:
The monthly rate of increase for Franklin's loan balance with an annual interest rate of 6% is represented by the expression 0.06/12, which equates to a monthly interest rate of 0.5%.
Step-by-step explanation:
The expression that reveals the monthly rate of increase for the loan balance when the annual interest rate is 6% is found by dividing the annual interest rate by the number of months in a year. To convert an annual rate to a monthly rate, you divide by 12 since there are 12 months in a year. Therefore, the correct expression for the monthly interest rate is 0.06/12, which is 0.005 or 0.5% per month.