Two cars \( A \) and \( B \) are moving in the same direction along a straight line with speeds \( 100 \, \text{km/h} \) and \( 80 \, \text{km/h} \), respectively such that car \( A \) is moving ahead of car \( B \). A person in car \( B \) throws a stone with a speed \( v \) so that it hits the car \( A \) with a speed of \( 5 \, \text{m/s} \). The value of \( v \) is ________ \( \text{km/h} \).
