Please use the simplex technique to find out the optimal solution for:
f(x1,x2,x3,x4,x5,x6) = -x1 - x2 - x3, subject to
2x1 + x4 = 1
2x2 + x5 = 1
2x3 + x6 = 1
and x_i is greater than or equal to 0 for i = 1,...,6. The variables x4,x5, and x6 appear to be slack variables, introduced to obtain equality constraints.