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4)

$n[(A - B) \cup (B - A)] = 58$

$n[(A \cup B) - (A \cap B)] = 58$

$n(A \cup B) = 67$

$\therefore n(A \cap B) = 9$


$n(A \cup B) = n(A) + n(B) - n(A \cap B)$

$67 = 32 + n(B) - 9$

$n(B) = 44$