Translate the following inference to logic notation: If David climbs a mountain, then it is sunny. If it is late, then David is climbing a mountain. If Jessica drinks water, then it is late. If it is cold, then Jessica is drinking water. If it is sunny, then it is cold. Therefore it is late if and only if Jessica is drinking water.
p -> q. r -> p. s -> r. t -> s. q -> t. Therefore r <-> s.