Rewrite the verbal argument below as a propositional wff argument, using the statement letters given. Then use propositional logic to prove that the argument is valid. If the birds are flying south and the leaves are turning, then it must be fall. Fall brings cold weather. The leaves are turning but the weather is not cold. Therefore, the birds are not flying south. (B = birds flying south; L = leaves turning; F = it is Fail; C = cold weather)