6. Consider the feasible region shown below. Assume the origin (A) is feasible and the constraints are all constraints and the variables are all nonnegative. Suppose you wish to maximize x1+x2+x3 over this feasible region and you are currently at point E. Which variable should enter the basis in the first iteration of the simplex algorithm if we wish to maximize the objective function improvement after the first iteration? x1 ondy x2 only x3 only x1,x2,orx3