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: It is snowing or Charles is working. Robert is playing tennis. It is not snowing. If Robert plays tennis, then Barbara is climbing a mountain.
Barbara is climbing a mountain can be inferred via the modus ponens rule. Charles is working can be inferred via the disjunctive syllogism rule. Robert is playing tennis and it is not snowing can be inferred via the conjunction rule. It is not snowing and Robert is playing tennis can be inferred via the conjunction rule.