Shrewsbury Technologies, which manufactures high$-$technology instruments for spacecraft, is considering the sale of a navigational unit to a private company that wishes to launch its own communications satellite. The company plans to purchase $8$ units, although it would also consider buying $16$ units. Shrewsbury has started a chart relating labor time required to units produced:

$\backslash$table$[[$Unit Produced,Time Required to$],[(x),$Produce the $x$ th Unit$],[1,8,000$ hours$],[2,7,200$ hours$],[4,6,480$ hours$],[8,?$