Consider the following premises. For all x_6, if x_6 takes a plane, then x_6 is climbing a mountain. For all x_6, if x_6 climbs a mountain, then x_6 is an office clerk. For all x_6, x_6 will take a plane or x_6 is an office clerk. There is at least one x_6 for which if x_6 were an office clerk, then x_6 is climbing a mountain. Can we infer the following from them? If we can, name the inference rule being used: For all x_6, x_6 will not climb a mountain.
 From the fact that there is at least one x_6 for which if x_6 were an office clerk, then x_6 is climbing a mountain, and that for all x_6, if x_6 climbs a mountain, then x_6 is an office clerk we can infer that there is at least one x_6 for which x_6 is an office clerk if and only if x_6 will climb a mountain via existential biconditional introduction. From the fact that there is at least one x_6 for which x_6 is an office clerk if and only if x_6 will climb a mountain we can infer that there is at least one x_6 for which if x_6 were an office clerk, then x_6 is climbing a mountain via existential biconditional elimination. Finally, from the fact that for all x_6, if x_6 takes a plane, then x_6 is climbing a mountain, that there is at least one x_6 for which if x_6 were an office clerk, then x_6 is climbing a mountain, and that for all x_6, x_6 will take a plane or x_6 is an office clerk we can infer that there is at least one x_6 for which x_6 will climb a mountain via existential disjunction elimination, which contradicts that For all x_6, x_6 will not climb a mountain. Therefore, the answer is no.