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: Barbara is a sailor or Mary is not climbing a mountain. For all x_14, x_14 will climb a mountain if and only if x_14 will write a letter.
If Mary climbs a mountain, then Barbara is a sailor can be inferred via the rewriting rule. For all x_14, if x_14 climbs a mountain, then x_14 is writing a letter can be inferred via the universal biconditional elimination rule. For all x_14, if x_14 writes a letter, then x_14 is climbing a mountain can be inferred via the universal biconditional elimination rule.