A company's E$-$commerce business has been increasing over the last $4$ months. The volume of units shipped from the e$-$commerce warehouse is shown below. This facility is experiencing $\_\_\_\_\_\_\_\_\_\_\_\_\_.($Slide $8)$

Month Units Shipped Processing Cost Cost per Unit

$110,000$ $$4,500$ $$0\mathrm{.}45$

$215,000$ $$6,000$ $$0\mathrm{.}40$

$318,000$ $$7,020$ $$0\mathrm{.}39$

$422,000$ $$7,920$ $$0\mathrm{.}36$