Calculate the amount spent on the party duration:
Total cost - cost of food = cost of party duration
$322.54 - $200.58 = $121.96
Divide the cost of party duration by the cost per hour:
Cost of party duration / cost per hour = party duration
$121.96 / $30.49 ≈ 4 hours (rounded to nearest hour)
Therefore, the party was approximately 4 hours long. So the answer is D. 4 hours.