Sets And Relations

Let \(\mathrm{A}=\{1,3,4,6,9\}\) and \(\mathrm{B}=\{2,4,5,8,10\}\). Let \(\mathrm{R}\) be a relation defined on \(\mathrm{A} \times \mathrm{B}\) such that \(\mathrm{R}=\left\{\left(\left(a_{1}, b_{1}\right),\left(a_{2}, b_{2}\right)\right): a_{1} \leq b_{2}\right.\) and \(\left.b_{1} \leq a_{2}\right\}\). Then the number of elements in the set R is :