Consider the following premises. For all x_12, if x_12 works, then x_12 is a taxi driver. There is at least one x_12 for which x_12 will work if and only if x_12 is an electrician. For all x_12, if x_12 works, then x_12 is an electrician. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_12 for which if x_12 were an electrician, then x_12 is a taxi driver.
 From the fact that there is at least one x_12 for which x_12 will work if and only if x_12 is an electrician we can infer that there is at least one x_12 for which if x_12 were an electrician, then x_12 is working via existential biconditional elimination. From the fact that for all x_12, if x_12 works, then x_12 is an electrician, and that there is at least one x_12 for which if x_12 were an electrician, then x_12 is working we can infer that there is at least one x_12 for which x_12 will work if and only if x_12 is an electrician via existential biconditional introduction. From the fact that there is at least one x_12 for which x_12 will work if and only if x_12 is an electrician we can infer that there is at least one x_12 for which if x_12 were an electrician, then x_12 is working via existential biconditional elimination. Finally, from the fact that there is at least one x_12 for which if x_12 were an electrician, then x_12 is working, and that for all x_12, if x_12 works, then x_12 is a taxi driver we can infer that there is at least one x_12 for which if x_12 were an electrician, then x_12 is a taxi driver via existential transitivity. Therefore, the answer is yes.