Given types of items of different values and volumes, find the most valuable set of items that fit in a knapsack of fixed volume. The number of items of each type is unbounded. This is an NP-hard combinatorial optimization problem. Formal Definition: There is a knapsack of capacity c > 0 and N types of items. Each item of type t has value v_t > 0 and weight w_t > 0. Find the number n_t > 0 of each type of item such that they fit, ∑_t=1^N n_tw_t ≤ c, and the total value, ∑_t=1^N n_tv_t, is maximized.