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: It is cold or Michael is not writing a letter. Michael is writing a letter if and only if it is cold. For all x_17, x_17 will not write a letter.
If Michael writes a letter, then it is cold can be inferred via the rewriting rule. If Michael writes a letter, then it is cold can be inferred via the biconditional elimination rule. If it is cold, then Michael is writing a letter can be inferred via the biconditional elimination rule.