According to the bureau of Navel Standards, 75% of all people are "inners" (that is , their belly buttons poke inwardly); everyone else is and "outer". let the random variable x be the number of outers amoung 7 randomly selected persons.

a. find the mean and variance of x

b. find the probabiility that exactly 2 of the 7 persons are outers.

c. find the probability that no more than 6 of the 7 are outers.

d. find the probability that none of the 7 is an outer.

need direction. thanks.