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_7, x_7 will take a plane or x_7 is not a mechanic. For all x_7, x_7 is a mechanic or x_7 will sleep. There is at least one x_7 for which x_7 will take a plane if and only if x_7 will sleep.
For all x_7, if x_7 were a mechanic, then x_7 is taking a plane can be inferred via the universal rewriting rule. There is at least one x_7 for which if x_7 takes a plane, then x_7 is sleeping can be inferred via the existential biconditional elimination rule. There is at least one x_7 for which if x_7 sleeps, then x_7 is taking a plane can be inferred via the existential biconditional elimination rule.