Solve the following problem graphically :
Minimise and Maximise Z = 3x + 9y
subject to the constraints :
`x + 3y le 60`
`x + y ge 10`
`x le y`
`x ge 0, y ge 0`

Answer

Minimum value = 60 at (5, 5) and maximum value = 180 at (15, 15) or (0, 20)