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: Jennifer is not writing a letter. For all y, y will write a letter if and only if y will sleep. If Jennifer writes a letter, then Jennifer is sleeping.
For all y, if y writes a letter, then y is sleeping can be inferred via the universal biconditional elimination rule. For all y, if y sleeps, then y is writing a letter can be inferred via the universal biconditional elimination rule.