Matchpoint company produces 3 types of tennis balls: heavy duty, regular, and extra duty, with a profit contribution of $24, $12, and $36 per gross (12 dozen), respectively. The linear programming formulation is: max. 24x1 + 12x2 + 36x3 subject to: .75x1 + .75x2 + 1.5x3 _ 300 (manufacturing) .8x1 + .4x2 + .4x3 _ 200 (testing) x1 + x2 + x3 _ 500 (canning) x1, x2, x3_ 0 where x1, x2, x3 refer to heavy duty, regular, and extra duty balls (in gross).

How much would you be willing to pay for an extra man-hour of testing capacity? For how many additional man-hours of testing capacity is this marginal value valid? Why?