An urn contains 7 yellow chips, 4 white chips, and 10 green chips. Four chips are to be selected one at a time and without replacement (wtr). a. Find the probability that exactly two of the four chips...

An urn contains 7 yellow chips, 4 white chips, and 10 green chips. Four chips are to be selected one at a time and without replacement (wtr).
a. Find the probability that exactly two of the four chips selected are green.
b. Find the probability that exactly two yellow and two white chips are drawn.