Show that corresponding to any basic feasible solution to the perturbed system of Exercise 15, which is nondegenerate for some range of  > 0, and to a vector ak not in the basis, there is a unique...

Show that corresponding to any basic feasible solution to the perturbed system of Exercise 15, which is nondegenerate for some range of
 > 0, and to a vector ak not in the basis, there is a unique vector ai in the basis which when replaced by ak leads to a basic feasible solution; and that solution is nondegenerate for a range of
 > 0.