The next phase in product development was to construct two or three prototype vehicles. Several important lessons were learned from the construction of these prototypes. First, any components that were difficult to assemble were identified. Typically, these components or the assemblies into which they fitted were redesigned to improve the ease of assembly. Second, assembly times could now be estimated quite accurately. In the third stage of value engineering, the effect of these redesigns on the target costs of components was determined and assembly target cost were identified. The output of this stage of value engineering was called the final target cost (see Exhibit 9). It differed from the draft target cost in two ways. First, it included assembly costs and second, the indirect manufacturing cost. The indirect manufacturing costs were assigned to products using the same the same procedures as the firm’s cost system. Thus, the final target cost for a model variant was expected to be equal to its reported product cost during manufacture.