Final answer:
Nan's idea, which is valuable and useful but not very novel, would be categorized as an improvement in the Neck Idea Generation Matrix.
Step-by-step explanation:
Based on the Neck Idea Generation Matrix, if Nan has an idea that is high on value and usefulness but low on degree of novelty, the idea has the quality of improvement. This is because the matrix categorizes ideas not only based on their novelty but also on their value and usefulness to the market or society. An improvement typically involves incrementally enhancing or refining an existing product, system, or process rather than creating something entirely new, as with an invention, or something that completely alters the market, as with innovation.