How do you allocate the vehicle/lane managment in Gas station such a way that in a given day maximum number of vehicles are allowed to fill the gas.

1. There are 4 lanes with each having two gas filling spots
2. If a bus comes to fill the gas. It can be accomodated only one per lane
3. Any vehicles is on the second gas filling spot in a lane has to wait till first gas filling spot is completed.

Let us assume following vehicles wait time

1. Bus - 6mins
2. Car - 4mins
3. Motor Bike - 2mins