What is the speed of a photon with respect to another photon if (a) the two photons are going in the same direction and (b) they are going in opposite directions?

What is the speed of photon in free space?

When a photon stimulates the emission of another photon the two photon have

When a photon stimulates the emission of another photon the two photon have

Point A and B are 90km apart from each other on a highway.A car starts from A and another from B at the same time.If they go in the same direction they meet in 9 hours and if they go in opposite directions they meet in 9/7 hours. Find their speeds.