Nick works at a digital appliances manufacturing company. Recently, he invented an adapter for televisions, which when connected would reduce the electricity consumption by half. This adapter worked with the earlier television models that the company manufactured, so the company was able to sell this product to their existing customers and to all their new customers. This is an example of a$($n$)\_\_\_\_\_\_\_\_$ innovation. a$.$ radical. b$.$ discontinuous. c$.$ architectural. d$.$ component.