You are designing a rectangular poster to contain $72$ in$.{?}^2$ of printing with a $4-$in$.$ margin at the top and bottom and a $2-$in$.$ margin at each side. What overall dimensions will minimize the amount of paper used?

What is the vertical height of the poster that will minimize the amount of paper used?

$h=in.$

What is the horizontal width of the poster that will minimize the amount of paper used?

$w=in.$