Problem $3-14($Static$)$

Demand for stereo headphones and MP$3$ 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 this year was as follows:

$\backslash$table$[[$MONTH$,$DEMAND $($UNITS$)],[$January$,4,200],[$February$,4,300],[$March$,4,000],[$April$,4,400],[$May$,5,000],[$June$,4,700],[$July$,5,300],[$August$,4,900],[$September$,5,400],[$October$,5,700],[$November$,6,300],[$December$,6,000]]$

a$.$ Using linear regression analysis, what would you estimate demand to be for each month next year? Using a spreadsheet, follow the general format in Exhibit $3\mathrm{.}8.($Do not round intermediate calculations. Round your answers to $2$ decimal places.$)$

$\backslash$table$[[$Month$,$Forecast$],[$January$,],[$February$,],[$March$,],[$April$,],[$May$,],[$June$,],[$July$,],[$August$,],[$September$,],[$October$,],[$November$,],[$December$,]]$

b$.$ To be reasonably confident of meeting demand, Nina decides to use three 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.$)$