Ahigh school janitor has 140 keys on his key chain. of these 140 keys, 100 open classroom doors, 80
open the door to the teachers' lounge, and 60 open classroom doors and the teachers' lounge. using this
information, answer each of the following questions.
let c be the event that a randomly selected key opens a classroom and i be the event that a randomly
selected key opens the teachers' lounge.
what is p(c), the probability that a key opens a classroom?
what is p(t), the probability that a key opens the teachers' lounge?
what is pc and t), the probability that a key opens a classroom and the teachers' lounge?
what is pc or t), the probability that a key opens a classroom or the teachers' lounge?

First, think of what you know. you know that the number t the end of the equation will need to be subtracted because it is the money he lost from buying the lawn mower. and your first two weeks have negative profit, so that tells you that c and d are wrong. now you can plug any of the weeks into a and b to see which one works. i'll start with plugging week 1 into a.this isn't right because it says your answer for week one should be -90.so now we need to try the same thing with b.this one got you the right answer, (sometimes if you only check with one of the weeks multiple will work so you need to check with more of the weeks, but it worked out fine here)this means that b is the correct answer.let me know if you need more clarification. i hope this : )