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 will not write a letter or x_15 will sleep. If it is cold, then David is not an electrician. For all x_15, if x_15 plays squash, then x_15 is an electrician. For all x_15, if x_15 sleeps, then x_15 is an electrician. For all x_15, x_15 will write a letter or x_15 will play squash.
For all x_15, x_15 will play squash or x_15 will sleep can be inferred via the universal resolution rule.