Consider the following premises. If David were a taxi driver, then Patricia is running. If Patricia goes running, then Richard is driving a car. If Patricia goes running, then David is a taxi driver. Can we infer the following from them? If we can, name the inference rule being used: If David were a taxi driver, then Richard is driving a car.
 From the fact that if David were a taxi driver, then Patricia is running, and that if Patricia goes running, then David is a taxi driver we can infer that David is a taxi driver if and only if Patricia is running via biconditional introduction. From the fact that David is a taxi driver if and only if Patricia is running we can infer that if David were a taxi driver, then Patricia is running via biconditional elimination. Finally, from the fact that if David were a taxi driver, then Patricia is running, and that if Patricia goes running, then Richard is driving a car we can infer that if David were a taxi driver, then Richard is driving a car via transitivity. Therefore, the answer is yes.