Consider the following problem: maximize subject to 2x1 + x2 + 6x3 - 4x4 x +2x + 4x3 2x1 +3x2 - X3 + X3 X3, X420 a) Find a basic solution with the basic variables as x1, x2, and x4. b) Is this solution feasible? c) Is this solution optimal? d) If it is not optimal, then starting with this solution find an optimal solution. X1 X1, X2, X4 6 X4 12 X4 2