Consider the following premises. For all x_9, x_9 will play squash or x_9 will not read a book. For all x_9, if x_9 plays squash, then x_9 is climbing a mountain. For all x_9, if x_9 were fast, then x_9 is reading a book. For all x_9, if x_9 climbs a mountain, then x_9 is fast. Can we infer the following from them? For all x_9, x_9 is fast if and only if x_9 will play squash.
 From the fact that for all x_9, if x_9 plays squash, then x_9 is climbing a mountain, and that for all x_9, if x_9 climbs a mountain, then x_9 is fast we can infer that for all x_9, if x_9 plays squash, then x_9 is fast. From the fact that for all x_9, x_9 will play squash or x_9 will not read a book we can infer that for all x_9, if x_9 reads a book, then x_9 is playing squash. From the fact that for all x_9, if x_9 were fast, then x_9 is reading a book, and that for all x_9, if x_9 reads a book, then x_9 is playing squash we can infer that for all x_9, if x_9 were fast, then x_9 is playing squash. Finally, from the fact that for all x_9, if x_9 were fast, then x_9 is playing squash, and that for all x_9, if x_9 plays squash, then x_9 is fast we can infer that for all x_9, x_9 is fast if and only if x_9 will play squash. Therefore, the answer is yes.