a telephone link is to be constructed beween 2 towns that are situated on opposite banks of a river at points A and B. The width of the river is 1 kilometer and B lies 2 kilometers downstream from A. It cost c $ per kilometer to contruct a line over land and 2c $ per kilometer under water. The telephone line will follow the river bank from A for a distance x (kilometers) and then will cross the river diagonnally in a straight line directly to B. Determine the total cost of the line as a function of x.... I have no idea as to how I am suppose to start solving this problem. PLEASE HELP! THANKS.