A bag contains 7 red balls, some blue balls and 3 black balls. Probability of picking two balls from the bag is 1/3such that one is exactly red and one is exactly blue. The probability of picking two blue balls from the bag is ______.

I. \(\frac{2}{21} \)

II. \(\frac{17}{42}\)

III. \(\frac{2}{7}\)