Consider the following premises. If Sarah takes a plane, then Jessica is a politician. For all x_13, x_13 is a politician if and only if x_13 will drive a car. If Jessica drives a car, then William is fast. Can we infer the following from them? If Sarah takes a plane, then William is fast.
 From the fact that for all x_13, x_13 is a politician if and only if x_13 will drive a car we can infer that for all x_13, if x_13 were a politician, then x_13 is driving a car. From the fact that for all x_13, if x_13 were a politician, then x_13 is driving a car we can infer that if Jessica were a politician, then Jessica is driving a car. From the fact that if Sarah takes a plane, then Jessica is a politician, and that if Jessica were a politician, then Jessica is driving a car we can infer that if Sarah takes a plane, then Jessica is driving a car. Finally, from the fact that if Sarah takes a plane, then Jessica is driving a car, and that if Jessica drives a car, then William is fast we can infer that if Sarah takes a plane, then William is fast. Therefore, the answer is yes.