Consider the following premises. For all x_13, x_13 is not curious. Jennifer is a scientist if and only if Charles is fast. Charles is fast if and only if it is cloudy. For all x_13, x_13 is curious if and only if x_13 is a scientist. Can we infer the following from them? If we can, name the inference rule being used: It is cloudy.
 From the fact that for all x_13, x_13 is curious if and only if x_13 is a scientist, and that for all x_13, x_13 is not curious we can infer that for all x_13, x_13 is not a scientist via universal biconditional elimination. From the fact that for all x_13, x_13 is not a scientist we can infer that Jennifer is not a scientist via universal instantiation. From the fact that Jennifer is a scientist if and only if Charles is fast, and that Jennifer is not a scientist we can infer that Charles is not fast via biconditional elimination. Finally, from the fact that Charles is fast if and only if it is cloudy, and that Charles is not fast we can infer that it is not cloudy via biconditional elimination, which contradicts that It is cloudy. Therefore, the answer is no.