Final answer:
The product life cycle concept has been proven to be a valid idea, and new analytical tools now provide "rules" for detecting points in the cycle.
Step-by-step explanation:
The subject of this question is Business.
It is discussing the concept of product development and the use of analytical tools to detect points in the cycle.
This is a relevant topic in the field of business as it relates to the process of bringing a product to market and improving it over time.