Okay so here is the work now that slot has opened up.
You have 6 people preparing bags and 900 bags. If the work is split, then you have 900/6 = 150 bags per person. Now the time it takes to do one bag is 2 minutes so 150*2 = 300 minutes for each person to do 150 bags. Therefore it takes 300 minutes to be done, which is 5 hours.