Solve the following goal programming model graphically and by using the computer:

minimize P1d +

1 , P2d -

2 , P3d -

3 subject to 4x1 + 2x2 + d -

1 - d +

1 = 80 x1 + d -

2 - d +

2 = 30 x2 + d -

3 - d +

3 = 50 xj, d -

i , d +

i Ú 0 LO.1