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_7, if x_7 goes running, then x_7 is a writer. There is at least one x_7 for which x_7 is a writer if and only if x_7 is a musician. For all x_7, x_7 will play squash or x_7 is a musician. For all x_7, x_7 will not play squash or x_7 will go running.
For all x_7, x_7 is a musician or x_7 will go running can be inferred via the universal resolution rule. There is at least one x_7 for which if x_7 were a writer, then x_7 is a musician can be inferred via the existential biconditional elimination rule. There is at least one x_7 for which if x_7 were a musician, then x_7 is a writer can be inferred via the existential biconditional elimination rule.