There are four variables: x1, x2, x3, x4.
If you choose either x3 or x4 or both – then you should chose exactly one of x1 or x2.
If you choose neither x3 or x4 – then there is no restriction in ch0osing x1 or x2.
I have come up with the following if else logic for this, but cannot proceed from there.
Can you let me know how to come up with a integer linear program with this understanding?