Feasible flow ($Bf=b,\ell \le f\le u$)

A feasible flow satisfies every flow balance and every capacity interval of a network problem. Feasibility is distinct from optimality: capacitated flow optimality conditions additionally certify that no allowed balanced flow displacement reduces the cost. With only one independent graph cycle, every balanced flow is determined by a single cycle parameter, and its feasible set is the intersection of the induced parameter intervals.