Identifying differences between the current state and the goal state and selecting operations that reduce these differences. The price of a notebook is four times the price of a pencil. One pencil costs 30 cents less than the notebook. This maybe due to the limited capacity of working memory. None of the above.
All poisonous things are bitter.
Arsenic is not bitter. Therefore, arsenic is not poisonous. Time away from a problem provides new insights, or otherwise facilitates, the problem solving process.