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 x_13, if x_13 sleeps, then x_13 is a musician. For all x_13, if x_13 were a musician, then x_13 is taking a plane. There is at least one x_13 for which x_13 is an office clerk if and only if x_13 will sleep. For all x_13, if x_13 takes a plane, then x_13 is an office clerk.
For all x_13, if x_13 sleeps, then x_13 is taking a plane can be inferred via the universal transitivity rule. For all x_13, if x_13 were a musician, then x_13 is an office clerk can be inferred via the universal transitivity rule. There is at least one x_13 for which if x_13 were an office clerk, then x_13 is sleeping can be inferred via the existential biconditional elimination rule. There is at least one x_13 for which if x_13 sleeps, then x_13 is an office clerk can be inferred via the existential biconditional elimination rule.