Problem 1. (15 points) Use only the tree method to either show that the following arguments are valid, or else find a counterexample. a. AV (BAC) 4 (CAB) b. If Mary had a lamb and the lamb was little, then Mary took care of the lamb. of Mary did not take care of the lamb, then if the lamb was not little the fox did not take care of the lamb. If the fox did not take care of the lamb, the fox went hungry. Mary had a lamb. The fox did not go hungry. Therefore, both Mary and the fox took care of the lamb