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: If William plays squash, then Mary is a police officer. William is playing squash or Elisabeth is not writing a letter. If Mary were a police officer, then Elisabeth is writing a letter.
If William plays squash, then Elisabeth is writing a letter can be inferred via the transitivity rule. If Elisabeth writes a letter, then William is playing squash can be inferred via the rewriting rule.