k1 = 0.9 ; k2 = 2.5 _1 = k1 _2 = k2	x3 - _1 x1 = 0 x4 - _2 x2 = 0 x1 + x2 = 1 x3 + x4 = 1
z = 0.5 V = (z - x1) / (x3 - x1)