In the following problem, suppose the resource values of the second and the third constraints are kept at 18 and 16, respectively, and that by the resource value for the first constraint, is allowed to vary from its value of 12. Over what range can b, vary without a change in the set of basic variables? Discuss your answer using the graphical procedure and simplex tableau. Max Z = 12x7 + 5x2 Subject to: 4x1 + 3x2.