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: If Karen writes a letter, then Thomas is driving a car. For all z_4, z_4 will drive a car if and only if z_4 is bored. If Thomas were bored, then it is not late. It is late. If Thomas drives a car, then Karen is writing a letter.
Thomas is not bored can be inferred via the modus tollens rule. For all z_4, if z_4 drives a car, then z_4 is bored can be inferred via the universal biconditional elimination rule. For all z_4, if z_4 were bored, then z_4 is driving a car can be inferred via the universal biconditional elimination rule.