There are four traffic lights on a stretch of road and the distance between each traffic light is 300 m. There is a 10-s lag time between successive green lights: The second light turns green 10 s after the first light turns green, the third light turns green 10 s after the second light does (and, thus, 20 s after the first light turns green), and so on. Each light stays green for 15 s. Having watched this sequence for some time, you understand that you can drive through the stretch of road at a range of constant speeds. You drive through the first light right when it turned green. What is the fastest speed that you can drive through the stretch of road without running any red lights? What is the slowest speed?