A box of nine iPhone 7 cellphones contains two red cellphones and seven black cellphones.

a. 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 both cellphones selected will be red?

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 red cellphone and one black cellphone selected?

c. If three cellphones are selected, with replacement (the cellphones are returned to the box after they are selected), what is the probability that all three will be red?

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)?