Two cars \( A \) and \( B \) each of mass \( 10^{3} \, \text{kg} \) are moving on parallel tracks separated by a distance of \( 10 \, \text{m} \), in same direction with speeds \( 72 \, \text{km/h} \) and \( 36 \, \text{km/h} \). The magnitude of angular momentum of car \( A \) with respect to car \( B \) is _______ \( \text{J·s} \).