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: There is at least one x_15 for which x_15 will write a letter or x_15 is a nurse. For all x_15, x_15 is a nurse if and only if x_15 is a musician. For all x_15, x_15 is not a musician. For all x_15, x_15 will not write a letter or x_15 will drive a car. For all x_15, if x_15 listens to a song, then x_15 is not driving a car.
There is at least one x_15 for which x_15 is a nurse or x_15 will drive a car can be inferred via the existential resolution rule. For all x_15, if x_15 were a nurse, then x_15 is a musician can be inferred via the universal biconditional elimination rule. For all x_15, if x_15 were a musician, then x_15 is a nurse can be inferred via the universal biconditional elimination rule. For all x_15, x_15 is not a nurse can be inferred via the universal biconditional elimination rule.