When I work out from the piovt rows 2, 3 & 4 work out the same and I not sure about x,y,z &w being non negative, some of my values are negative.

The routes are to be one way which means x,y,z &w are to be non negative.

Attempted Solution =

+1 +2 -1 +1 x 30

+2 -1 +1 +1 y 60 (R2 - R4)

+3 -3 +2 +2 z 70 (R3 - 3R4)

+2 +8 -4 +2 w 80 (R4 - R4)

+1 +2 -1 +1 x 30

+0 -9 -5 -1 y -20

+0 -9 +5 -1 z -20 (R3 - R2)

+0 -9 -5 +1 w 20 (R4 + R3)

+1 +2 -1 +1 x 30

+0 -9 -5 -1 y -20

+0 0 +10 0 z 0 (R3 - R2)

+0 0 0 +2 w 0 (R4 + R3)