Hello,

I've been challenged on the university with this problem, which i can't resolve it. Can somebody help me? It needs to be resolved with propositional logic methods.

This is the problem:

Twelve University professors and students have been in the library at the time when a very expensive book

on propositional logic has disappeared. Each one entered once,stayed some time and left. If two of

them were in the library at the same time then at least one saw the other. Police interviewed these

students and professors and gathered the following evidence:

-Semsaid that he saw Bryan andZeldain the library.

-Caitlinswore that she sawGeorgeandHolly.

-Bryansaid that he sawSemandVanessa.

-Mariaclaimed that she sawDavidandVanessa.said that he saw

- NicolasAlexanderandJana.

-Davidsaid that he sawBryanandZelda.

-Hollyclaimed that she sawNicolasandJana.

-Zeldatestified that she sawBryanandMaria.

-Georgesaid that he sawAlexanderandJana.

-Vanessasaid that she sawMariaandZelda.-

Alexandersaid that he sawGeorgeandCaitlinin the library.

-Janasaid that she sawHollyandCaitlin.

Which one of the twelve University affiliates is not telling the truth? What he/she should have said

so that it doesn’t get caught?