The birth rate of newborns in BC Women hospital in the month of March is represented in the following table:X $($year$)20052006200720082009$y $($sales$)1219293745$a$)$ Determine the linear regression equation for the given data.b$)$ Use the regression equation as a model to estimate the birth rate of newborns in $2012.$c$)$ Determine how good is the coefficient determination.