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: Linda is not a mechanic. If Linda climbs a mountain, then Linda is a server. For all y_3, y_3 is a server if and only if y_3 is a mechanic.
For all y_3, if y_3 were a server, then y_3 is a mechanic can be inferred via the universal biconditional elimination rule. For all y_3, if y_3 were a mechanic, then y_3 is a server can be inferred via the universal biconditional elimination rule.