Consider the following premises. David is sleeping if and only if Michael is a taxi driver. For all x_12, x_12 is a lawyer if and only if x_12 is a taxi driver. David is sleeping or Michael is a lawyer. Can we infer the following from them? Michael is a taxi driver.
 From the fact that for all x_12, x_12 is a lawyer if and only if x_12 is a taxi driver we can infer that Michael is a lawyer if and only if Michael is a taxi driver. From the fact that Michael is a lawyer if and only if Michael is a taxi driver we can infer that if Michael were a lawyer, then Michael is a taxi driver. From the fact that David is sleeping if and only if Michael is a taxi driver we can infer that if David sleeps, then Michael is a taxi driver. Finally, from the fact that if David sleeps, then Michael is a taxi driver, that if Michael were a lawyer, then Michael is a taxi driver, and that David is sleeping or Michael is a lawyer we can infer that Michael is a taxi driver. Therefore, the answer is yes.