City B is 10 miles downstream from city A. City A is 5 miles south of the river, and city B is 20 miles north of the river. The river is 2 miles wide. Where should we build a bridge across the river...

City B is 10 miles downstream from city A. City A is 5 miles south of the river, and city B is 20 miles north of the river. The river is 2 miles wide. Where should we build a bridge across the river to make the travel distance between cities A and B as small as possible? Can you generalize this result?

A cylindrical soda can has a volume of 20 cubic inches. What height and diameter minimize the surface area of the can? Can you generalize this result?