(a) Suppose we know that \( A^{\prime}=\{g, p, r, x\} \). Then what would \( A \) have to be?
Identify the universal set and the complement of \( A \).
The universal set is \( U = \{g, h, p, q, r, x, y\} \), and \( A^{\prime} = \{g, p, r, x\} \).
Find \( A \) by taking the complement of \( A^{\prime} \).
\( A = U - A^{\prime} = \{h, q, y\} \).
\[
\boxed{A = \{h, q, y\}}
\]
(b) Suppose \( C=\{h, p, q, y\} \). Then what is \( C^{\prime} \)?
Identify the universal set and the set \( C \).
The universal set is \( U = \{g, h, p, q, r, x, y\} \), and \( C = \{h, p, q, y\} \).
Find \( C^{\prime} \) by taking the complement of \( C \).
\( C^{\prime} = U - C = \{g, r, x\} \).
\[
\boxed{C^{\prime} = \{g, r, x\}}
\]
\[
\boxed{A = \{h, q, y\}}
\boxed{C^{\prime} = \{g, r, x\}}
\]