Consider the following premises. For all x_13, x_13 will climb a mountain. There is at least one x_13 for which x_13 will climb a mountain if and only if x_13 will play tennis. Can we infer the following from them? For all x_13, neither x_13 will play tennis nor x_13 is a taxi driver.
 From the fact that there is at least one x_13 for which x_13 will climb a mountain if and only if x_13 will play tennis we can infer that there is at least one x_13 for which if x_13 climbs a mountain, then x_13 is playing tennis. From the fact that there is at least one x_13 for which if x_13 climbs a mountain, then x_13 is playing tennis, and that for all x_13, x_13 will climb a mountain we can infer that there is at least one x_13 for which x_13 will play tennis. Finally, from the fact that there is at least one x_13 for which x_13 will play tennis we can infer that there is at least one x_13 for which x_13 will play tennis or x_13 is a taxi driver, which contradicts that For all x_13, neither x_13 will play tennis nor x_13 is a taxi driver. Therefore, the answer is no.