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: Thomas is excited if and only if Linda is writing a letter. Linda is not sleeping. For all y_4, y_4 will climb a mountain if and only if y_4 is excited. For all x_14, x_14 will sleep if and only if x_14 will write a letter.
If Thomas were excited, then Linda is writing a letter can be inferred via the biconditional elimination rule. If Linda writes a letter, then Thomas is excited can be inferred via the biconditional elimination rule. For all y_4, if y_4 climbs a mountain, then y_4 is excited can be inferred via the universal biconditional elimination rule. For all x_14, if x_14 sleeps, then x_14 is writing a letter can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 were excited, then y_4 is climbing a mountain can be inferred via the universal biconditional elimination rule. For all x_14, if x_14 writes a letter, then x_14 is sleeping can be inferred via the universal biconditional elimination rule.