Vite fais s'il te plait?

The correct answer is: C) 4.57$

If you pay at the beginning of the month, the interest for that month is calculated on the remaining debt ($2,475.59), while if you pay at the end of the same month, the interest is calculated on the total debt ($2,875.59).

Therefore, the difference on the amount of interest will be the interest on the amount you pay at the beginning of the month ($400.00).

The APR is an annual rate, therefore, in order to calculate the interest, you need to find the monthly rate, dividing by the months in one year:
r = APR / 12 

The interest will be:
i = A × r
  = A × (APR / 12)
  = 400 × (0.137 / 12)
  = 4.567

Hence, the difference in the amount of interest accrued by the end of the month if you pay at the beginning of the month versus the end of the month is option C) 4.57$