Suppose \( A \) and \( B \) are the coefficients of \( 30^{\text{th}} \) and \( 12^{\text{th}} \) terms respectively in the binomial expansion of \( (1 + x)^{2n-1} \). If \( 2A = 5B \), then \( n \) is equal to:
\( 22 \)
\( 21 \)
\( 19 \)
\( 20 \)