$4.$ PharmaDev develops and markets new technological products used in health care. PharmaDev$$s products are developed in a two$-$step process: invention of new technology and development of a product based on that technology. When new technology is invented at PharmaDev$$s R&D department, PharmaDev files for a patent. Patents are granted for a period of $12$ years starting from the date of issue. Once a patent is issued, a new health care product based on the patented technology is developed at one of PharmaDev$$s three independent product development centers. After product development is complete, the new product is then launched to the market. Each product is developed at only one center, and each center can only develop a single patented product at a time. On average, PharmaDev receives a new patent every $5$ months $($with standard deviation of $5$ months$).$ The product development process lasts $12$ months on average $($with standard deviation of $24$ months$).$ The newly patented technologies wait in PharmaDev$$s internal queue in the order of their patent issue dates, until one of the development centers becomes ready for new product development and pulls the first one from the queue. On average, how many years of patent life are left for a new product when it is launched to the market?