I want to write two constraints by using “or” :

“There may be at most Y distribution centers or Z processing centers or both to be selected.”

```
Specific2..sum((i,t), y(i,t))=l=Y or sum(k, z(k))=l=Z;
```

But I cannot write it. Could you please help me.

I recommend studying section about logical modeling in the excellent book by HP Williams (https://www.wiley.com/en-us/Model+Building+in+Mathematical+Programming%2C+5th+Edition-p-9781118443330. Basically, make two equations, introduce binary variables that control if an equation holds and then make sure at least one of the binary variable is 1.

-Michael