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_15, x_15 is a scientist or x_15 is not a musician. For all x_15, x_15 is a scientist if and only if x_15 will work. For all x_15, x_15 is a musician.
For all x_15, if x_15 were a musician, then x_15 is a scientist can be inferred via the universal rewriting rule. For all x_15, if x_15 were a scientist, then x_15 is working can be inferred via the universal biconditional elimination rule. For all x_15, if x_15 works, then x_15 is a scientist can be inferred via the universal biconditional elimination rule.