I don't know how to start this:

class with n kids lines up for recess. The order in which the kids line up is random with each

ordering being equally likely. There are two kids in the class named Betty and Mary. The use of the

word "

or

" in the description of the events, should be interpreted as the inclusive or. That is "

A or B

"

means that

A

is true,

B

is true, or both

A

and

B

are true.

What is the probability that Betty is first in line or Mary is last in line as a function of

n? Simplify your final expression as much as possible and include an explanation of how you calculated this

probability.