Consider the following premises. Richard is drinking water if and only if Linda is playing squash. Linda is not playing squash. It is sunny if and only if Richard is drinking water. Can we infer the following from them? If we can, name the inference rule being used: It is sunny.
 From the fact that Richard is drinking water if and only if Linda is playing squash, and that Linda is not playing squash we can infer that Richard is not drinking water via biconditional elimination. Finally, from the fact that it is sunny if and only if Richard is drinking water, and that Richard is not drinking water we can infer that it is not sunny via biconditional elimination, which contradicts that It is sunny. Therefore, the answer is no.