Consider the following premises. For all x_11, x_11 is a cashier. For all x_11, x_11 will go running if and only if x_11 is a cashier. For all x_11, if x_11 were happy, then x_11 is running. Can we infer the following from them? There is at least one y_4 for which y_4 will go running.
 From the fact that for all x_11, x_11 will go running if and only if x_11 is a cashier we can infer that for all x_11, if x_11 were a cashier, then x_11 is running. From the fact that for all x_11, x_11 is a cashier we can infer that for all x_11, x_11 is a cashier or x_11 is happy. From the fact that for all x_11, if x_11 were a cashier, then x_11 is running, that for all x_11, if x_11 were happy, then x_11 is running, and that for all x_11, x_11 is a cashier or x_11 is happy we can infer that for all x_11, x_11 will go running. From the fact that for all x_11, x_11 will go running we can infer that Sarah is running. Finally, from the fact that Sarah is running we can infer that there is at least one y_4 for which y_4 will go running. Therefore, the answer is yes.