1. A man in a row boat at point P, 5 km from the nearest point A on a straight shore wishes to reasvch point B, 6 km along the shore from point A, in the shortest time. Where should he land if he can row 2km/hr and walk 4km/hr (Hint: pick a point on the shore line)?

2. An open rectangular tank (no top) with square ends is to have a volume of 6400 cubic meters. The base costs $75 per square meter and the sides $25 per square meter. What are the dimensions to build the tank at minimum cost?