Final answer:
The question is about probability without replacement from an urn with red, black, and green balls. A variable related to the number of balls of the chosen color is mentioned, but specific probabilities cannot be calculated without more information.
Step-by-step explanation:
The student appears to be asking about probability without replacement. The urn contains an unspecified number of red, black, and green balls, and a color is chosen at random before drawing balls. The letter b seems to represent a variable related to the number of balls of the chosen color. Without more information, a specific expression for b cannot be provided.
Regarding part b of the question, it introduces a binary variable that takes the value 1 if a selected ball is of the chosen color, and 0 otherwise. We would need to know the total number of balls and the number of balls of each color to determine the probability of drawing a ball of the chosen color. Then the expected value of this random variable could be calculated. However, key parts of the question are missing, so I cannot provide a reliable method for calculating this probability.
For example, in an urn with four red and three yellow balls, if three balls are drawn without replacement, the probability that one of each color is selected involves combinations and probabilities of different drawing sequences. The specific question asked cannot be answered without additional information regarding the quantity of each color of balls in the urn.