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 it rains, then James is writing a letter. For all x, x is happy. Susan is excited or it is raining. Susan is excited if and only if James is writing a letter.
If Susan were excited, then James is writing a letter can be inferred via the biconditional elimination rule. If James writes a letter, then Susan is excited can be inferred via the biconditional elimination rule.