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 it snows, then Mary is an astronaut. For all x_15, if x_15 were an astronaut, then x_15 is making tea. Karen is taking a plane if and only if it is snowing.
If Karen takes a plane, then it is snowing can be inferred via the biconditional elimination rule. If it snows, then Karen is taking a plane can be inferred via the biconditional elimination rule.