Consider the following premises. For all x_7, x_7 will take a plane if and only if x_7 is an electrician. Joseph is not taking a plane. Joseph is an electrician or it is sunny. Can we infer the following from them? If we can, name the inference rule being used: It is not sunny.
 From the fact that for all x_7, x_7 will take a plane if and only if x_7 is an electrician we can infer that Joseph is taking a plane if and only if Joseph is an electrician via universal instantiation. From the fact that Joseph is taking a plane if and only if Joseph is an electrician, and that Joseph is not taking a plane we can infer that Joseph is not an electrician via biconditional elimination. Finally, from the fact that Joseph is an electrician or it is sunny, and that Joseph is not an electrician we can infer that it is sunny via disjunctive syllogism, which contradicts that It is not sunny. Therefore, the answer is no.