A single channel queue forms at the entrance to an off-street parking area. Arrivals are random, at an average rate of 10.7 vehicles per minute, and the time required for the service process of removing the time-card from the control box and driving past the boom gate is also random and averages 2 seconds per vehicle. 

In order to accommodate the queuing vehicles in 90% of cases, which option below best represents the storage space in front of the boom barrier? Assuming M/M/1 queueing model.