Consider the following premises. If it is not cold, then David is climbing a mountain. Patricia is an artist if and only if it is cold. For all x_14, x_14 is not an artist. Can we infer the following from them? If we can, name the inference rule being used: David is climbing a mountain.
 From the fact that for all x_14, x_14 is not an artist we can infer that Patricia is not an artist via universal instantiation. From the fact that Patricia is an artist if and only if it is cold, and that Patricia is not an artist we can infer that it is not cold via biconditional elimination. Finally, from the fact that if it is not cold, then David is climbing a mountain, and that it is not cold we can infer that David is climbing a mountain via modus ponens. Therefore, the answer is yes.