The IET Company has maintained an $80\%$ service level policy for inventory of foam rollers. Mean

demand during the reorder period is $160$ rollers, and the standard deviation is $50$ rollers. The annual

cost of carrying one roller in inventory is $$5.$ As a new business strategy, management decided it must

increase the service level and agreed to spend an extra $$300$ on inventory carrying costs. How much

does the service level increase with the extra $$300?$