Detailed Instructions: Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
Problem: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
Solution:
b