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_4, y_4 will not take a plane. For all y_4, y_4 will work if and only if y_4 will take a plane. For all y_4, y_4 will cook if and only if y_4 will work. There is at least one y_4 for which if y_4 plays squash, then y_4 is cooking.
For all y_4, if y_4 works, then y_4 is taking a plane can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 cooks, then y_4 is working can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 takes a plane, then y_4 is working can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 works, then y_4 is cooking can be inferred via the universal biconditional elimination rule. For all y_4, y_4 will not work can be inferred via the universal biconditional elimination rule.