text: ... ____ .... _____\n . / ........ &#92; ... / ........ &#92;\nP -------- OH ==== BC\n . &#92; ____ / ... &#92; ____ /\n\nGoing to BC there are 3 x 4 different ways = 12\n\nGoing back again there are now only 3 x 2 different ways as you have already traversed one of the roads on each leg on the way down to BC\n\nThus total number of different ways = 4 x 3 x 3 x 2 = 72