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_12, x_12 is an astronaut or x_12 is a doctor. For all x_12, if x_12 writes a letter, then x_12 is not drinking water. For all x_12, if x_12 were a sailor, then x_12 is drinking water. For all x_12, if x_12 were a doctor, then x_12 is drinking water. There is at least one x_12 for which x_12 is not an astronaut or x_12 is a sailor.
There is at least one x_12 for which x_12 is a doctor or x_12 is a sailor can be inferred via the existential resolution rule.