Consider the following premises. John is a cashier if and only if Charles is happy. John is a bartender or John is a cashier. Charles is happy or John is not a bartender. Can we infer the following from them? Charles is not happy.
 From the fact that Charles is happy or John is not a bartender we can infer that if John were a bartender, then Charles is happy. From the fact that John is a cashier if and only if Charles is happy we can infer that if John were a cashier, then Charles is happy. Finally, from the fact that if John were a bartender, then Charles is happy, that if John were a cashier, then Charles is happy, and that John is a bartender or John is a cashier we can infer that Charles is happy, which contradicts that Charles is not happy. Therefore, the answer is no.