Consider the following premises. Robert is not a mechanic or it is sunny. Barbara is not a bartender or Robert is a taxi driver. If it is sunny, then Charles is playing squash. Robert is a taxi driver if and only if Charles is playing squash. Robert is a mechanic or Barbara is a bartender. Can we infer the following from them? If we can, name the inference rule being used: Charles is not playing squash.
 From the fact that Robert is a mechanic or Barbara is a bartender, and that Robert is not a mechanic or it is sunny we can infer that Barbara is a bartender or it is sunny via resolution. From the fact that Barbara is a bartender or it is sunny, and that Barbara is not a bartender or Robert is a taxi driver we can infer that it is sunny or Robert is a taxi driver via resolution. From the fact that Robert is a taxi driver if and only if Charles is playing squash we can infer that if Robert were a taxi driver, then Charles is playing squash via biconditional elimination. Finally, from the fact that if it is sunny, then Charles is playing squash, that if Robert were a taxi driver, then Charles is playing squash, and that it is sunny or Robert is a taxi driver we can infer that Charles is playing squash via disjunction elimination, which contradicts that Charles is not playing squash. Therefore, the answer is no.