There are six red balls and three black balls in a box. All nine balls are identical except their color. Nick claims that he can pull out six balls (without replacement)

and that all six will be red. Assuming that he has no magical skills and he chooses at random, let x be the probability that he will succeed. He then pulls out a ball and it turns out to be red. At that stage, the probability that he will succeed has been increased, compared with the original probability x, by

(a) 10%

(b) 15%

(c) 16.67%

(d) 25%

(e) 50%