A new computer system is put in place at a toll booth.
The system comes online at 9:00am (with no vehicles in the queue) and vehicles arrive at a rate of ?(t) = 12 - 0.4t (with ?(t) in veh/min and t in min).
Due to a computer system failure, cars are not serviced until 9:10am.
Between 9:10 and 9:20 they are serviced at 3 veh/min. After 9:20 they are serviced at 15 veh/min.
Assuming D/D/1 queuing, what is the total vehicle delay in veh-min?