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: Joseph is playing squash if and only if it is late. Joseph is fast if and only if Joseph is playing squash. Joseph is fast or it is not late.
If it is late, then Joseph is fast can be inferred via the rewriting rule. If Joseph plays squash, then it is late can be inferred via the biconditional elimination rule. If Joseph were fast, then Joseph is playing squash can be inferred via the biconditional elimination rule. If it is late, then Joseph is playing squash can be inferred via the biconditional elimination rule. If Joseph plays squash, then Joseph is fast can be inferred via the biconditional elimination rule.