Consider a packaging facility that packages some product delivered to the facility by trucks. Every day, trucks arrive evenly from 8am to 4pm and unload 40 units of unpackaged product per hour at a small warehouse attached to the packaging facility. The assembly process takes unpackaged items from the warehouse and spends 3 minutes to package each item. The packaged items are shipped out immediately to retail stores. The warehouse can hold up to 120 units of the product. Once the warehouse is full, the trucks have to hold the items and wait its turn to unload items it carries. The facility continues to run until all the items delivered in a day are all packaged.

According to the above information, what is the average waiting time of a trck that has to wait?

O 30 minutes

O 45 minutes

O1 hour

0 2 hours