What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all x_12, if x_12 writes a letter, then x_12 is playing tennis. There is at least one x_12 for which if x_12 were an artist, then x_12 is not playing tennis. For all x_12, if x_12 were a server, then x_12 is playing tennis. For all x_12, x_12 is an artist or x_12 will climb a mountain. For all x_12, x_12 is a server or x_12 will write a letter.
For all x_12, x_12 will play tennis can be inferred via the universal disjunction elimination rule.