You are designing a tool for a maritime response unit to act when a possible crash is foreseen. Two ships are on the same route in opposite directions one towards the other. The red ship leaves Harbor A at time 0h traveling at a speed of r knots. The blue ship leaves Harbor B at the same time, sailing at a speed of b knots. The distance in kilometers between the harbors is given.

Assuming that speeds are constant, determine how many minutes it will take for the ships to encounter each other.