We have been given than M1 to M4 policies are to be applied across Security Zone, Restricted Zone and Public Zone.
Important to note that each policy will be applied at least once across the 3 zones.
Now there are certain constraints that need to be kept in mind
1. M1 must be applied to Security Zone. - Okay
2. If M2 is applied in "Public Zone", then M3 will also be applied in the "Public Zone" - Okay
3. M4 is not applied if M1 is applied - Now this gives us clearly that in Security Zone, M4 is not applied.
4. If M3 is applied to restricted Zone than M1 must also be applied to Restricted Zone - Which means that M4 will not be applied to Restricted zone (provided M3 is applied)
5. And no more than 2 policies can be applied to each zone
Now, with the constraints above, what must be true and what cannot be true:
1. M2 and M4 are both applied to the Public Zone. - Think about it, if M2 is applied to public zone, then M3 will also be applied to the zone (Constraint 2 above). And then M4 is also applied making M2, M3 and M4 in the same zone.
Cannot be true - restricted by constraint 5 above.2. If M2 is applied to Restricted Zone, M4 must be applied to public zone. - If M2 is applied to RZ, M4 can be applied or it may not be applied. There are no constraints around M2 and Restricted Zone together. Hence, this statement is not a "Must be True" or "Cannot be True"
3. If M3 is applied in RZ, M4 must be applied to Public Zone (PZ).- Think about it, as per constraint 4 above, M4 will not be applied in RZ because M1 will be applied. M4 cannot be applied in Security Zone (SZ) because M1 is applied as per constraint 1. And the policy must be present in atleast one of the zone making M4 a must be for Public Zone
- Hence, must be true4. M4 is applied to RZ - Can be true or cannot be. We don't know and there are no specific constrains around the 2.
5. If M1 is applied to RZ then M3 is also applied to RZ. - No always true. The constraint is that if M3 is applied to RZ, M1 must be not the other way around. M1 can be standalone applied to RZ without needing M3.