Consider the following LP:

Maximize z = c1 x1 + c2 x2 + c3 x3 + c4 x4 subject to p1 x1 + p2 x2 + p3 x3 + p4 x4 = b x1, x2, x3, x4 Ú 0 The vectors p1, p2, p3, and p4 are shown in Figure 7.4. Assume that the basis B of the current iteration is comprised of p1 and p2.

(a) If the vector p1 enters the basis, which of the current two basic vectors must leave in order for the resulting basic solution to be feasible?

(b) Can the vector p4 be part of a feasible basis?