There are three types of manufacturing costs, direct materials, direct labor, and manufacturing overhead. direct materials and direct labor are able to be traced directly to units of product. manufacturing overhead is not. why not? how is manufacturing overhead applied to products?

Zara, a global retail and apparel manufacturer based in spain that has successfully implemented this idea by having a continuous flow of new products that are typically limited in supply. zara has created a system that draws its clientèle into its stores, on average, 17 times per year as compared to 4 times per year for most stores. how is zara using it to gain competitive advantage? what specific technologies are used by zara to maintain this advantage over its competition?