Consider the following premises. For all x_6, if x_6 climbs a mountain, then x_6 is happy. There is at least one x_6 for which x_6 will climb a mountain. For all x_6, if x_6 were a taxi driver, then x_6 is happy. For all x_6, if x_6 were happy, then x_6 is a taxi driver. Can we infer the following from them? There is at least one x_6 for which x_6 is happy.
 From the fact that there is at least one x_6 for which x_6 will climb a mountain we can infer that there is at least one x_6 for which x_6 will climb a mountain or x_6 is a taxi driver. From the fact that for all x_6, if x_6 were happy, then x_6 is a taxi driver, and that for all x_6, if x_6 were a taxi driver, then x_6 is happy we can infer that for all x_6, x_6 is happy if and only if x_6 is a taxi driver. From the fact that for all x_6, x_6 is happy if and only if x_6 is a taxi driver we can infer that for all x_6, if x_6 were a taxi driver, then x_6 is happy. Finally, from the fact that for all x_6, if x_6 climbs a mountain, then x_6 is happy, that for all x_6, if x_6 were a taxi driver, then x_6 is happy, and that there is at least one x_6 for which x_6 will climb a mountain or x_6 is a taxi driver we can infer that there is at least one x_6 for which x_6 is happy. Therefore, the answer is yes.