Let \( R \) be a relation from the set \( \{1,2,3,\ldots,60\} \) to itself such that \( R=\{(a,b): b=pq \text{ , where } p,q\ge 3 \text{ are prime numbers}\} \). Then, the number of elements in \( R \) is:
\( 600 \)
\( 660 \)
\( 540 \)
\( 720 \)