Why does the government issue patents? The government issues patents A. to prevent firms from keeping secret how a product is made. B. to ensure that new products are safe and effective for consumers. C. to encourage firms to spend money on the research and development necessary to create new products. D. to encourage competition among firms in markets with barriers to entry. E. to limit excessive economic profits in the short run before new firms have had time to enter profitable markets. How long do patents last? A patent is the exclusive right to a product for a period of nothing years from the date the patent is filed with the government. (Enter your response as an integer.)