Consider the following premises. For all x_13, x_13 is an electrician or x_13 is a musician. There is at least one x_13 for which x_13 will take a plane. For all x_13, x_13 will make tea. For all x_13, if x_13 were an electrician, then x_13 is not taking a plane. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_13 for which x_13 will make tea and x_13 is a musician.
 From the fact that for all x_13, if x_13 were an electrician, then x_13 is not taking a plane, and that there is at least one x_13 for which x_13 will take a plane we can infer that there is at least one x_13 for which x_13 is not an electrician via existential modus tollens. From the fact that for all x_13, x_13 is an electrician or x_13 is a musician, and that there is at least one x_13 for which x_13 is not an electrician we can infer that there is at least one x_13 for which x_13 is a musician via existential disjunctive syllogism. Finally, from the fact that for all x_13, x_13 will make tea, and that there is at least one x_13 for which x_13 is a musician we can infer that there is at least one x_13 for which x_13 will make tea and x_13 is a musician via existential conjunction. Therefore, the answer is yes.