\( A = \{2, 3, 5, 7\} \) and
\( B = \{2, 5, 8, 9\} \)
The union of \( A \) and \( B \) is \( A \cup B = \{2, 3, 5, 7, 8, 9\} \).
Now, the cardinality of a power set is \( 2^n \), where \( n \) is the number of elements in the original set.
Since \( A \cup B \) has \( 6 \) elements, the cardinality of its power set is \( 2^6 = 64 \).