7...Demand for stereo headphones and MP3 players for joggers has caused Nina Industries 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:

MONTH DEMAND (UNITS)

January 4,100

February 4,200

March 3,900

April 4,300

May 4,900

June 4,600

July 5,200

August 4,800

September 5,300

October 5,600

November 6,200

December 5,900

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.)

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 intermediate calculations. Round your answer to the nearest whole number.)