If one light beam is heading toward you from the right, and another is heading toward you from the left, how quickly from the perspective of the right-moving beam is the left-moving beam approaching it?

If a taxi is racing toward you from the north at $\frac{3}{4}c$ and another taxi is racing toward you from the south at $\frac{1}{2}c$, how quickly from the perspective of one taxi is the other approaching? (Note: This exercise is close, but not identical, to an exercise encountered earlier: In the earlier version, you considered how quickly the distance between the taxis was closing, from your stationary perspective. In this exercise, you are considering the perspective of the taxi drivers.)