Let the sum of two positive integers be \( 24 \). If the probability, that their product is not less than \( \frac{3}{4} \) times their greatest possible product, is \( \frac{m}{n} \), where \( \gcd(m,n) = 1 \), then \( n - m \) equals:
\( 8 \)
\( 9 \)
\( 10 \)
\( 11 \)
