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 Joseph is not a sailor. For all x_12, x_12 is a sailor if and only if x_12 is fast. It is cloudy if and only if it is cold. It is not cloudy.
If Joseph were a sailor, then it is cold can be inferred via the rewriting rule. If it is cloudy, then it is cold can be inferred via the biconditional elimination rule. If it is cold, then it is cloudy can be inferred via the biconditional elimination rule. It is not cold can be inferred via the biconditional elimination rule. For all x_12, if x_12 were a sailor, then x_12 is fast can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 were fast, then x_12 is a sailor can be inferred via the universal biconditional elimination rule.