Answer
(a) Yes.
(b) $X=w_1$, $X=w_2$
(c) $X=b_2$, $X=w_2$
Work Step by Step
Use the configuration given in Example 3.3.11, we have:
(a) Yes. Because it is true that $b_1$ is above $w_1$.
(b) This question asks which block(s) has/have a white color, thus we have the answer: $X=w_1$, $X=w_2$
(c) This question asks which block(s) is/are above $b_3$, thus we have the answer: $X=b_2$, $X=w_2$
