15. If you are randomly sampling one at a time with replacement from a bag that contains eight blue marbles, seven red marbles, and fi ve green marbles, what is the probability of obtaining

a. A blue marble in one draw from the bag?

b. Three blue marbles in three draws from the bag?

c. A red, a green, and a blue marble in that order in three draws from the bag?

d. At least two red marbles in three draws from the bag? other