You are in charge of a quarry that supplies sand and stone aggregates to your company's construction sites. Empty trucks from construction sites arrive at the quarry's huge piles of sand and stone aggregates and wait in line to enter the station, which can load either sand or aggregate. At the station they are filled with material, weighed, checked out, and proceed to a construction site. currently, 8 empty trucks arrive per hour, on average. once a truck has entered a loading station, it takes 6 minutes for it to be filled, weighed, and checked out. concerned that trucks are spending too much time waiting and being filled, you are evaluating two alternatives to reduce the average time the trucks spend in the system. The first alternative is to add side boards to the trucks, and to add a helper at the loading station, at a total cost of 50,000. The arrival rates of the trucks would change to 6 per hour, and the filling time would be reduced to 4 minutes. The second alternative is to add another loading station at a cost of 80,000. The trucks would wait in a common line and the truck at the front of the line would move to the next available station. The average waiting time under the current system and the two alternatives are how many minutes?