Suppose there are 4 Starting Points A, B, C, and D and 4 Destination Points namely P, Q, R, and S. Let M be a common point to all the routes, i.e. the possible bus routes are AMP, AMQ, AMR AMS BMP, BMQ, BMR BMS…… DMR and DMS i.e. 4 x 4 or sixteen bus routes. There are four bus routes starting from each of A, B, C, and D.