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_1, if x_1 were a mechanic, then x_1 is reading a book. There is at least one x_1 for which x_1 is a musician if and only if x_1 is a mechanic. For all x_1, x_1 will not read a book.
For all x_1, x_1 is not a mechanic can be inferred via the universal modus tollens rule. There is at least one x_1 for which if x_1 were a musician, then x_1 is a mechanic can be inferred via the existential biconditional elimination rule. There is at least one x_1 for which if x_1 were a mechanic, then x_1 is a musician can be inferred via the existential biconditional elimination rule.