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: Robert is climbing a mountain if and only if Patricia is writing a letter. Patricia is writing a letter if and only if Robert is climbing a mountain.
If Robert climbs a mountain, then Patricia is writing a letter can be inferred via the biconditional elimination rule. If Patricia writes a letter, then Robert is climbing a mountain can be inferred via the biconditional elimination rule. If Patricia writes a letter, then Robert is climbing a mountain can be inferred via the biconditional elimination rule. If Robert climbs a mountain, then Patricia is writing a letter can be inferred via the biconditional elimination rule.