Anchor: Even if he could build a computer out of what was obtainable, there would be no way to power it.
Entailed: Even if it was possible for him to create a computer out of what he had, there would be no power source for it.
Contradiction: He knew he'd be able to power the computer, if only he could build one.
Contradiction: I know that you have no idea what I am talking about.
Contradiction: The kayak is floating.
Contradiction: I still work at a restaurant. 
Contradiction: Two men on a boat.