The following digraph depicts a partially solved minimum cost flow problem with labels on nodes indicating net demand and those on arcs showing unit cost, capacity, and current flow.

(a) Verify that the given solution is a basic feasible solution for basis 511, 22, 11, 32, 12, 426.

(b) Compute all simplex directions available at this basis.

(c) Determine whether each of the simplex directions is improving.

(d) Regardless of whether they are improving, determine the maximum feasible step l that could be applied to each of the simplex directions.