An urn contains 10 red balls and 20 green balls. (a) Suppose 15 balls are drawn from the urn with replacement. What is the probability that exactly 4 of the balls are red? (b) Now suppose 15 balls are drawn without replacement. What is the probability that exactly 4 of the balls are red?
a) 165/1024, 231/323
b) 231/1024, 165/323
c) 165/1024, 231/511
d) 231/1024, 165/511
