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: For all y, y will make tea if and only if y is a nurse. There is at least one y for which y is sad if and only if y is a nurse. For all y, y is not sad. For all y, y is an artist if and only if y will make tea.
For all y, if y makes tea, then y is a nurse can be inferred via the universal biconditional elimination rule. For all y, if y were an artist, then y is making tea can be inferred via the universal biconditional elimination rule. There is at least one y for which if y were sad, then y is a nurse can be inferred via the existential biconditional elimination rule. For all y, if y were a nurse, then y is making tea can be inferred via the universal biconditional elimination rule. For all y, if y makes tea, then y is an artist can be inferred via the universal biconditional elimination rule. There is at least one y for which if y were a nurse, then y is sad can be inferred via the existential biconditional elimination rule. There is at least one y for which y is not a nurse can be inferred via the existential biconditional elimination rule.