# Programming an interaction

Certainly due to my lack of competence this code

```
pol = polygon([(0,0), (0,10), (10,10), (0,0)], fill=True, rgbcolor=(0.81,0.81,0.81))
g = plot(x,(0,10),color="blue",ymin=0,ymax=10)
@interact
def _(c=slider(0,1,step_size=0.2,default=.5),inac=checkbox(True,"Domaine Inaccessible")):
a = solve(-c*x+6==x, x)
aa = a[0].right()
h = plot(-c*x+6,(aa, 6),color="green",ymin=0,ymax=10)
graph = h+g
if inac :
graph += pol
show(graph)
```

conplains that `graph`

is not defined.

Is there some thing I have not understood in the construction of `@interact`

?