Answer
(a) Yes.
(b) $X=g$
(c) $X=b_1, X=w_1$
Work Step by Step
Use the configuration given in Example 3.3.11, we have:
(a) Yes. Because it is true that $w_2$ is above $b_3$.
(b) This question asks which block(s) has/have a gray color, thus we have the answer: $X=g$
(c) This question asks $g$ is above which block(s), thus we have the answer: $X=b_1, X=w_1$
