The following sample observations were randomly selected. $($Round intermediate calculations and final answers places.$)$

$\backslash$table$[[x$:$,4,4,3,6,8],[y$:$,5,6,5,7,7]]$

pictureClick here for the Excel Data File

a$.$ The regression equation is hat$(y)=$

b$.$ When $x$ is $7$ this gives hat$(y)$