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_6, if x_6 were a doctor, then x_6 is an astronaut. For all x_6, x_6 is a doctor or x_6 is a musician. For all x_6, x_6 is an astronaut or x_6 is not a musician.
For all x_6, if x_6 were a musician, then x_6 is an astronaut can be inferred via the universal rewriting rule.