Presupposition or entailment?

Decide whether in the following examples the second sentence is a presupposition or an entailment of the first one.

a) John managed to stop smoking. John stopped smoking. (:vips 7584:)

b) Bill is a better linguist than Mary. Mary is a linguist. (:vips 7585:)

c) My cousin teaches English and French at the community college. My cousin teaches English at the community college. (:vips 7586:)