Select a subset of the following set of objects subject to a weight limit of 20 lbs such that the total value is maximized. The items are specified by corresponding weight in lbs and value in dollars. The items must be chosen as a whole. (20) Item: 1 2 3 4 5 6 Weight in lbs: 4 2 5 6 9 8 Value in Dollars: 19 9 20 28 45 39