Consider the following premises. For all x, x is an electrician or x will not take a plane. For all x, if x were an electrician, then x is taking a plane. If Elisabeth were an electrician, then it is snowing. Can we infer the following from them? If we can, name the inference rule being used: If Elisabeth takes a plane, then it is snowing.
 From the fact that for all x, x is an electrician or x will not take a plane we can infer that for all x, if x takes a plane, then x is an electrician via universal rewriting. From the fact that for all x, if x takes a plane, then x is an electrician, and that for all x, if x were an electrician, then x is taking a plane we can infer that for all x, x will take a plane if and only if x is an electrician via universal biconditional introduction. From the fact that for all x, x will take a plane if and only if x is an electrician we can infer that for all x, if x takes a plane, then x is an electrician via universal biconditional elimination. From the fact that for all x, if x takes a plane, then x is an electrician we can infer that if Elisabeth takes a plane, then Elisabeth is an electrician via universal instantiation. Finally, from the fact that if Elisabeth takes a plane, then Elisabeth is an electrician, and that if Elisabeth were an electrician, then it is snowing we can infer that if Elisabeth takes a plane, then it is snowing via transitivity. Therefore, the answer is yes.