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: William is not playing squash. William is a musician or it is sunny. William is a musician if and only if William is playing squash.
If William were a musician, then William is playing squash can be inferred via the biconditional elimination rule. If William plays squash, then William is a musician can be inferred via the biconditional elimination rule. William is not a musician can be inferred via the biconditional elimination rule.