Consider the following premises. For all x_5, if x_5 works, then x_5 is a scientist. There is at least one x_5 for which x_5 will not work. For all x_5, x_5 will work if and only if x_5 is a scientist. Can we infer the following from them? For all x_5, x_5 is a scientist.
 From the fact that for all x_5, x_5 will work if and only if x_5 is a scientist we can infer that for all x_5, if x_5 were a scientist, then x_5 is working. From the fact that for all x_5, if x_5 works, then x_5 is a scientist, and that for all x_5, if x_5 were a scientist, then x_5 is working we can infer that for all x_5, x_5 will work if and only if x_5 is a scientist. Finally, from the fact that for all x_5, x_5 will work if and only if x_5 is a scientist, and that there is at least one x_5 for which x_5 will not work we can infer that there is at least one x_5 for which x_5 is not a scientist, which contradicts that For all x_5, x_5 is a scientist. Therefore, the answer is no.