Anchor: Above the first 20 billion pieces, less attractive mail begins to presort and the postal service's costs at the margin undoubtedly begin to increase.
Entailed: Some of the mail that the postal service deals with is less attractive.
Contradiction: The postal service's costs will always decrease.
Contradiction: This is not subject to change.
Contradiction: Having a 401k is a good way to save money, so you should invest in one. 
Contradiction: In 1180, nothing of importance happened that year.
Contradiction: 90% of the population embraces Hinduism.