Final answer:
Executives, manufacturing employees, and salespeople are considered internal sources for new-product ideas, crucial for innovation and competitive advantage in the New Product Development process.
Step-by-step explanation:
Executives, manufacturing employees, and salespeople are all examples of internal sources for new-product ideas. Companies often rely on their own employees to come up with ideas for new products or improvements because they have a deep understanding of the business's processes, products, and market needs. The innovation process is reinforced by a firm's desire to remain competitive in the market, leading them to seek new ways to produce more cost-effectively or to create products that fulfill consumer demands. Furthermore, engaging cross-functional teams that include these employees is crucial in the New Product Development process to ensure diverse perspectives and expertise are utilized.