A flow in a residual network provides a roadmap for adding flow to the original flow network.If f is a flow in G and f is a flow in the corresponding residual network Gf,we define f t f',the augmentation of flow f by f',to be a function from V×VtoR,defined by (f↑f),)= f,)+f'(u,)-f'(w,0if(u,)∈E, (26.4) otherwise 12/12 12 11/16 15/20 5 4/9 8/13 4/4 8 11/14