Translate the following inference to logic notation: If it is overcast, then Robert is a poet. If it rains, then Elisabeth is a taxi driver. If Robert were a poet, then it is raining. If Elisabeth were a taxi driver, then it is overcast. If Elisabeth were a taxi driver, then it is raining. Therefore it is overcast if and only if Elisabeth is a taxi driver.
p -> q. r -> s. q -> r. s -> p. s -> r. Therefore p <-> s.