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: Elisabeth is playing a game if and only if Mary is taking a plane. It is sunny if and only if Elisabeth is a cashier. If Mary takes a plane, then it is sunny. Elisabeth is a cashier or Elisabeth is playing a game.
If Elisabeth plays a game, then Mary is taking a plane can be inferred via the biconditional elimination rule. If it is sunny, then Elisabeth is a cashier can be inferred via the biconditional elimination rule. If Mary takes a plane, then Elisabeth is playing a game can be inferred via the biconditional elimination rule. If Elisabeth were a cashier, then it is sunny can be inferred via the biconditional elimination rule.