To provide a greater certainty that the observed results are not by chance.
Yes-no question if your question was about way of asking.
If you mean a kind of question directly suggests answers, it could be directed issue or suggestive question. Am I right?
The answer is; neutral.
<em>Hope this helped! :)</em>
This would be a perfect example of the system of barter as you are trading one book for the other. You can see from here what barter is, a trading system which involves direct exchange of goods without some kind of medium of exchange, for example money. Services can also be traded this way.
