Demand for stereo headphones and MP3 players for joggers has caused Nina Industrles to grow almost 50 percent over the past year. The number of joggers continues to expand, so Nina expects demand for headsets to also expand, because, as yet, no safety laws have been passed to prevent joggers from wearing them. Demand for the players for last year was as follows: a. Using IInear regression analysis, what would you estimate demand to be for each month next year? (Do not round Intermedlate calculatlons. Round your answers to 2 decimal places.) b. To be reasonably confident of meeting demand, Nina decides to use 4 standard errors of estimate for safety. How many additional units should be held to meet this level of confidence? (Do not round Intermedlate calculations. Round your answer to the nearest whole number.)