Consider two cities `P` and `Q` berween which consistent bus servece is available in both directions. Every `x` mimutes `A` morning jogging towards `Q` from `P` wigh a speed of `10 km h^(-1)`. Every `18 mim` a bus crosses this jogger in its own direction of motion and every `6 min` another bus crosses in opposite derection. What is time prerilod between two consecutive buses and also find the speed of buses ?.