Consider the following premises. For all z_3, if z_3 were a musician, then z_3 is drinking water. For all z_3, z_3 will drink water or z_3 is not a musician. For all z_3, if z_3 drinks water, then z_3 is a musician. Can we infer the following from them? If we can, name the inference rule being used: There is at least one z_3 for which the fact that z_3 drinks water does not imply that z_3 is a musician.
 From the fact that for all z_3, if z_3 drinks water, then z_3 is a musician, and that for all z_3, if z_3 were a musician, then z_3 is drinking water we can infer that for all z_3, z_3 will drink water if and only if z_3 is a musician via universal biconditional introduction. From the fact that for all z_3, z_3 will drink water if and only if z_3 is a musician we can infer that for all z_3, if z_3 drinks water, then z_3 is a musician via universal biconditional elimination. From the fact that for all z_3, z_3 will drink water or z_3 is not a musician we can infer that for all z_3, if z_3 were a musician, then z_3 is drinking water via universal rewriting. From the fact that for all z_3, if z_3 drinks water, then z_3 is a musician, and that for all z_3, if z_3 were a musician, then z_3 is drinking water we can infer that for all z_3, z_3 will drink water if and only if z_3 is a musician via universal biconditional introduction. Finally, from the fact that for all z_3, z_3 will drink water if and only if z_3 is a musician we can infer that for all z_3, if z_3 drinks water, then z_3 is a musician via universal biconditional elimination, which contradicts that There is at least one z_3 for which the fact that z_3 drinks water does not imply that z_3 is a musician. Therefore, the answer is no.