Classify each cost item of Ripon Printers given below into one of the business functions of the value chain, either (1) R&D, (2) design of products and processes, (3) production, (4) marketing (including sales), (5) distribution, or (6) customer service. Item: a. depreciation of trucks used to transport books to college bookstores b. cost of the wood used to manufacture paper c. salary of the scientists attempting to find another source of printing ink d. cost of designing the book size so that a standard-sized box is filled to capacity.