A box of nine iPhone 5C cellphones (the iPhone “for the colorful”) contains two yellow cellphones and seven green cellphones.
a. If two cellphones are randomly selected from the box, with-out replacement (the first cellphone is not returned to the box ­after it is selected), what is the probability that both cellphones ­selected will be green?
b. If two cellphones are randomly selected from the box, without replacement (the first cellphone is not returned to the box after it is selected), what is the probability that there will be one yellow cellphone and one green cellphone selected?
c. If three cellphones are selected, with replacement (the cell-phones are returned to the box after they are selected), what is the probability that all three will be yellow?
d. If you were sampling with replacement (the first cellphone is ­returned to the box after it is selected), what would be the ­answers to (a) and (b)?