Task: Question Answering
Input (English): Problem: an urn contains 10 black and 5 white balls. two balls are drawn from the urn one after the other without replacement. what is the probability that both drawn balls are black ?
Options: a. 1 / 5, b. 3 / 7, c. 2 / 5, d. 3 / 5, e. 2 / 7
Output (English): b