$($a$)$ Innovation is a new idea, method, or process that adds value to the existing product or service. It is a change that makes things better. Innovation can be incremental or radical. Incremental innovation is a small change over time, while radical innovation is a major change all at once. Examples of incremental innovation are the introduction of new features or functions to existing products, such as the addition of GPS to smartphones. Examples of radical innovation are the introduction of new technologies, such as the invention of the Internet.

There are three types of innovation: incremental, breakthrough, and disruptive. Incremental innovation is the most common type of innovation. It is the process of making small changes to existing products or services over time. Breakthrough innovation is a major change in an existing product or service that creates a new market. Disruptive innovation is a new technology or process that disrupts an existing market.

$($b$)$ The rate at which a firm introduces innovations is determined by a number of factors, including the firm's culture, resources, and goals. The culture of the firm is important because it shapes the way that the firm thinks about innovation. A firm that values innovation is more likely to introduce new products and services. The resources of the firm are also important because they determine the amount of money and time that the firm can devote to innovation. The goals of the firm are also important because they determine the direction of the firm's innovation efforts.

$($c$)$ The closed innovation model is a model in which a firm keeps all of its innovations internal. This means that the firm does not share its innovations with its competitors. The open innovation model is a model in which a firm shares its innovations with its competitors. This means that the firm works with its competitors to develop new products and services.

$($d$)$ CAD $($Computer$-$Aided Design$)$ is a software program that helps designers create digital models of products. CAM $($Computer$-$Aided Manufacturing$)$ is a software program that helps manufacturers create physical products from digital models.

$($e$)3-$D printing is a process of creating physical objects from digital models. The object is created by printing layer upon layer of material until the object is complete. $3-$D printing is a disruptive innovation because it is a new technology that is changing the way that products are made.

$($f$)$ Disruptive innovations are new technologies that change the way that existing products or services are made. Disruptive innovations often start out as small, niche products or services, but they can eventually grow to become the dominant player in the market. $3-$D printing is a disruptive innovation because it is a new technology that is changing the way that products are made.

Final answer: In conclusion, innovation is a key driver of economic growth and competitiveness. It is important for firms to invest in innovation in order to remain competitive in the global market. There are a number of factors that determine the rate at which a firm introduces innovations, including the firm's culture, resources, and goals. The closed and open innovation model are two different approaches to innovation. CAD and CAM are two software programs that help designers and manufacturers create digital and physical products. $3-$D printing is a disruptive innovation that is changing the way that products are made.