Minimize z = 5x1 + 2x2 + 3x3 + y1 + 3y2 + 4y3 subject to
x1 + x2 + x3 <= 12
y1 + y2 + y3 <= 20
x1 + y1 >= 8
x2 + y2 >= 14
x3 + y3 >= 8
x1 >= 0
x2 >= 0
x3 >= 0
y1 >= 0
y2 >= 0
y3 >= 0