Consider the following premises. If Mary drinks water, then Richard is fast. If Richard were fast, then it is sunny. If it is sunny, then Thomas is playing squash. If Thomas plays squash, then it is sunny. Can we infer the following from them? If we can, name the inference rule being used: If Mary drinks water, then Thomas is playing squash.
 From the fact that if Mary drinks water, then Richard is fast, and that if Richard were fast, then it is sunny we can infer that if Mary drinks water, then it is sunny via transitivity. From the fact that if it is sunny, then Thomas is playing squash, and that if Thomas plays squash, then it is sunny we can infer that it is sunny if and only if Thomas is playing squash via biconditional introduction. From the fact that it is sunny if and only if Thomas is playing squash we can infer that if it is sunny, then Thomas is playing squash via biconditional elimination. Finally, from the fact that if Mary drinks water, then it is sunny, and that if it is sunny, then Thomas is playing squash we can infer that if Mary drinks water, then Thomas is playing squash via transitivity. Therefore, the answer is yes.