Let S = {a, b, c, d, e, f, g} be a collection of objects with benefit-weight values, a: (12, 4), b : (10, 6), c : (8, 5), d: (11, 7), e: (14, 3), f : (7, 1), g : (9, 6). What is an optimal solution to the fractional knapsack problem for S assuming we have a sack that can hold objects with total weight 18? Show your work.