Consider the following premises. For all z, z will make tea. For all z, if z makes tea, then z is playing squash. There is at least one z for which if z plays squash, then z is making tea. Can we infer the following from them? If we can, name the inference rule being used: There is at least one z for which z will play squash.
 From the fact that for all z, if z makes tea, then z is playing squash, and that there is at least one z for which if z plays squash, then z is making tea we can infer that there is at least one z for which z will make tea if and only if z will play squash via existential biconditional introduction. From the fact that there is at least one z for which z will make tea if and only if z will play squash we can infer that there is at least one z for which if z makes tea, then z is playing squash via existential biconditional elimination. Finally, from the fact that there is at least one z for which if z makes tea, then z is playing squash, and that for all z, z will make tea we can infer that there is at least one z for which z will play squash via existential modus ponens. Therefore, the answer is yes.