49. Wind blowing against a flat surface exerts a maximum force equal to kSv², where S is the area of the surface, v is the wind's velocity, and k is a constant. If a 40 mile-per-hour ( mph ) wind can exert a maximum force of 50 pounds on a 1-square-foot flat surface, what is the maximum force, in pounds, that an 80 mph wind can exert on a 2-square-foot flat surface?