Consider the following premises. If it snows, then Patricia is a taxi driver. If Patricia were a taxi driver, then it is snowing. If it snows, then Barbara is a poet. If Barbara were a poet, then Patricia is a taxi driver. Can we infer the following from them? It is snowing if and only if Patricia is a taxi driver.
 From the fact that if it snows, then Barbara is a poet, and that if Barbara were a poet, then Patricia is a taxi driver we can infer that if it snows, then Patricia is a taxi driver. From the fact that if Patricia were a taxi driver, then it is snowing, and that if it snows, then Patricia is a taxi driver we can infer that Patricia is a taxi driver if and only if it is snowing. From the fact that Patricia is a taxi driver if and only if it is snowing we can infer that if Patricia were a taxi driver, then it is snowing. Finally, from the fact that if it snows, then Patricia is a taxi driver, and that if Patricia were a taxi driver, then it is snowing we can infer that it is snowing if and only if Patricia is a taxi driver. Therefore, the answer is yes.