Consider Example 13.4-2.

(a) Will x4 = 0 in the optimum solution?

(b) For each of the following two cases, determine the feasible ranges for z1, z2, z3, x1, x2, and x3. (You will find it helpful to represent each situation as in Figure 13.10.)

(i) x1 = 3 and all the remaining data are the same.

(ii) x1 = 0, D1 = 5, D2 = 4, and D3 = 5.