Need help with section A and B

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 contunues 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 linear regression analysis, what would you estimate demand to be for each month next year? (Do not round intermediate calculations. Round your answers to 2 decimal places.) Answer is complete but not entirely correct. b. To be reasonably confident of meeting demand, Nina decides to use 4 standard errors of estimate for safety. How many addltional units should be held to meet this level of confidence? (Do not round intermedlate calculations. Round your answer to the nearest whole number.)