To find the estimated monthly expense, you can divide the quarterly payment by 3 (since there are three months in a quarter).
The quarterly payment is $163.92. So, the monthly expense would be:
\[ \text{Monthly Expense} = \frac{\text{Quarterly Payment}}{3} = \frac{163.92}{3} \approx 54.64 \]
This rounds to approximately $55.00.
Therefore, the correct response is:
$55.00