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 overcast if and only if Susan is a server. For all y_1, y_1 is a nurse if and only if y_1 is a server. It is not overcast.
If it is overcast, then Susan is a server can be inferred via the biconditional elimination rule. If Susan were a server, then it is overcast can be inferred via the biconditional elimination rule. Susan is not a server can be inferred via the biconditional elimination rule. For all y_1, if y_1 were a nurse, then y_1 is a server can be inferred via the universal biconditional elimination rule. For all y_1, if y_1 were a server, then y_1 is a nurse can be inferred via the universal biconditional elimination rule.