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 snowing or Michael is a taxi driver. If Michael writes a letter, then it is overcast. For all x_16, x_16 is a taxi driver if and only if x_16 will write a letter. If it snows, then Michael is writing a letter.
If Michael were a carpenter, then it is snowing can be inferred via the rewriting rule. For all x_16, if x_16 were a taxi driver, then x_16 is writing a letter can be inferred via the universal biconditional elimination rule. For all x_16, if x_16 writes a letter, then x_16 is a taxi driver can be inferred via the universal biconditional elimination rule.