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, x_6 is curious or x_6 will listen to a song. For all x_6, x_6 is happy or x_6 will not listen to a song. For all x_6, x_6 is a soldier. For all x_6, if x_6 were curious, then x_6 is happy.
For all x_6, if x_6 listens to a song, then x_6 is happy can be inferred via the universal rewriting rule.