Consider the following premises. For all x_11, x_11 will drive a car or x_11 will play squash. There is at least one x_11 for which x_11 will not play squash. For all x_11, x_11 will not drive a car or x_11 is a server. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_11 for which x_11 is a server or x_11 will write a letter.
 From the fact that for all x_11, x_11 will drive a car or x_11 will play squash, and that for all x_11, x_11 will not drive a car or x_11 is a server we can infer that for all x_11, x_11 will play squash or x_11 is a server via universal resolution. From the fact that for all x_11, x_11 will play squash or x_11 is a server, and that there is at least one x_11 for which x_11 will not play squash we can infer that there is at least one x_11 for which x_11 is a server via existential disjunctive syllogism. Finally, from the fact that there is at least one x_11 for which x_11 is a server we can infer that there is at least one x_11 for which x_11 is a server or x_11 will write a letter via existential addition. Therefore, the answer is yes.