Explanation:
First, we need to determine the total revenue from docking 100 boats:
$850 per boat x 100 boats = $85,000
Next, we need to determine the total cost of operating the boathouse:
$2200 (fixed cost) + $550 for each of the 100 boats = $77,200
Finally, we can calculate the monthly profit:
Revenue - Cost = $85,000 - $77,200 = $7,800
Therefore, the answer is option C: $27,800.