To calculate the monthly finance charge for the credit card transaction, we need to determine the average daily balance (ADB) for the month. The ADB is calculated by adding the daily balances for each day of the month and dividing by the number of days in the month.
First, we need to find the daily interest rate, which is the annual interest rate divided by the number of days in a year (365):
19% ÷ 365 = 0.0521% per day
Next, we need to determine the daily balance for each day of the month. Assuming that the balance was not changed during the month except for the $50 payment, the daily balances can be calculated as follows:
Days 1-21: $400
Days 22-30: $350 ($400 - $50 payment)
The ADB for the month is calculated as follows:
ADB = [(21 × $400) + (9 × $350)] ÷ 30
ADB = $12,050 ÷ 30
ADB = $401.67
Finally, we can calculate the monthly finance charge by multiplying the ADB by the daily interest rate and the number of days in the month:
Monthly finance charge = $401.67 × 0.0521% × 30
Monthly finance charge = $6.28
Therefore, the monthly finance charge for the credit card transaction is $6.28.