Consider the following premises. If Elisabeth were curious, then David is not an office clerk. David is an office clerk. For all x_7, x_7 is curious if and only if x_7 will sleep. Can we infer the following from them? If we can, name the inference rule being used: Elisabeth is not sleeping.
 From the fact that for all x_7, x_7 is curious if and only if x_7 will sleep we can infer that Elisabeth is curious if and only if Elisabeth is sleeping via universal instantiation. From the fact that if Elisabeth were curious, then David is not an office clerk, and that David is an office clerk we can infer that Elisabeth is not curious via modus tollens. Finally, from the fact that Elisabeth is curious if and only if Elisabeth is sleeping, and that Elisabeth is not curious we can infer that Elisabeth is not sleeping via biconditional elimination. Therefore, the answer is yes.