\f(a) The variables x1 and x; can serve as basic variables for a basic feasible solution. Show that the problem expressed with these as basic variables is x1 +3x3ZX4: 6 x2+2x3+4x4 2 x3 + in = 8+z (b) Entering x3 into the basis will reduce the value of 2:. Why? Show that the variable to be replaced is x2. (0) Perform the pivot operation. Show that the minimal value of the objective function is 7 and is achieved at (3,0, 1,0)