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: If Joseph were a cashier, then it is cloudy. David is making tea. John is a mechanic or Joseph is a cashier. If it is cloudy, then Susan is playing squash. John is not a mechanic.
If Joseph were a cashier, then Susan is playing squash can be inferred via the transitivity rule. Joseph is a cashier can be inferred via the disjunctive syllogism rule. David is making tea and John is not a mechanic can be inferred via the conjunction rule. John is not a mechanic and David is making tea can be inferred via the conjunction rule.