For some clarification and pointers thanks.
The telephone lines coming into a helpdesk are occupied 55% of the time
a. If you are calling this helpdesk, what is the probability that it will take you more than three calls to get through?
I believe this is 0.55^3?
b. If, in addition, a friend tries independently to contact the same helpdesk, what is the probability that it will require more than three calls between you?
Any pointers to help me get started here? thanks