



 
Hi Jackie, I am going to point you to a question we received a while ago that was
I used a tree diagram to solve this problem and I think that looking at it will help you with b) part of your problem but let's look at the counting principle first. In the lunch problem the students have 2 choices for a drink, 2 choices for a main course and 2choices for desert. As the student goes through the line she first chooses one of two drinks. Regardless of the drink she chooses she can choose one of two main courses. Thus at this point she has chosen one of 2 2 = 4 possibilities. Now, regardless of what is on her tray already she can choose one of two desserts. Thus in total there are 2 2 2 = 8 possible lunch combinations. If you now look at the tree diagram you will see all 8 possible lunch combinations. In the notation I used there they are {J, H, B}, {J, H, A}, {J, P, B}, and so on. This is the sample space, the list of all possible lunch combinations. I hope this helps,  


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