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_1, y_1 is an astronaut if and only if y_1 is happy. There is at least one y_1 for which y_1 is happy.
For all y_1, if y_1 were an astronaut, then y_1 is happy can be inferred via the universal biconditional elimination rule. For all y_1, if y_1 were happy, then y_1 is an astronaut can be inferred via the universal biconditional elimination rule.