An urn contains 26 balls, each of a different color (let’s
creatively call the colors c1, c2, . . . , c26). You draw four
balls in sequence from the urn. Each time you draw a ball, you
record the color of the ball, and return it to the urn. (That is,
each time you perform this experiment, you get a sequence of four
colors.)
(a) How many such four-color sequences are possible?
(b) What is the probability that a...