Given the linear programming problem below where X₁ represents the number of belts a company produces and X₂ represents the number of pairs of gloves produced. The first constraint is for the number of square yards leather available and the second for the number of hours of skilled labor available.

Max z = 4X₁ + 3X₂

s.t. X₁ + X₂ 40

2X₁ + X₂ 60

The solution is X₁ = X₂ = 20 with max Z = 140. The final tableau is shown below

Z	X1	X2	S1	S2	RHS	Basis
1	0	0	2	1	140	Z =140
0	0	1	2	-1	20	X2 = 20
0	1	0	-1	1	20	X1 = 20

Use this information to answer the following questions.

3. Show that if c2 is between 2 and 4 the current basis remains optimal.