Consider the following premises. Robert is not a mechanic. If Mary were an office clerk, then Robert is a mechanic. It is cloudy or John is a taxi driver. If it is cloudy, then Mary is an office clerk. Can we infer the following from them? If we can, name the inference rule being used: John is not a taxi driver.
 From the fact that if it is cloudy, then Mary is an office clerk, and that if Mary were an office clerk, then Robert is a mechanic we can infer that if it is cloudy, then Robert is a mechanic via transitivity. From the fact that if it is cloudy, then Robert is a mechanic, and that Robert is not a mechanic we can infer that it is not cloudy via modus tollens. Finally, from the fact that it is cloudy or John is a taxi driver, and that it is not cloudy we can infer that John is a taxi driver via disjunctive syllogism, which contradicts that John is not a taxi driver. Therefore, the answer is no.