The number of marbles of different colors stored in a hat is listed below:

4 red marbles
10 green marbles
7 blue marbles

Without looking in the hat, Dan takes out a marble at random. He replaces the marble and then takes out another marble from the hat. What is the probability that Dan takes out a blue marble in both draws?

2 / 21
1 / 9
1 / 2
2 / 3