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: There is at least one x_14 for which x_14 will write a letter if and only if x_14 will go running. For all x_14, if x_14 writes a letter, then x_14 is running. For all x_14, if x_14 were a poet, then x_14 is running. For all x_14, x_14 will write a letter.
For all x_14, x_14 will go running can be inferred via the universal modus ponens rule. There is at least one x_14 for which if x_14 writes a letter, then x_14 is running can be inferred via the existential biconditional elimination rule. There is at least one x_14 for which if x_14 goes running, then x_14 is writing a letter can be inferred via the existential biconditional elimination rule.