3. (6 points) A boy has 3 red marbles and 5 green marbles in his left pocket, and 5 red marbles and 4 green marbles in his right pocket. He drew two marbles (at a time) at random from his left pocket and put them into his right pocket. Afterwards, he drew a marble from his right pocket. Given that he drew a green marble from his right pocket, what is the conditional probability that he drew two green marbles from his left pocket?