A power house, P, is on one bank of a straight river $200$ m wide, and a factory, F, is on the opposite bank $400m$ downstream from P. The cable has to be taken across the river, under water at a cost of Rs $6/m$. On land the cost is Rs $ 3/m$. What path should be chosen so that the cost is minimized?
I first looked at the extreme cases and then tried to find the solution. But then too there was a problem