Sales A doughnut shop at a shopping mall sells a dozen doughnuts for $\$ 220$ . Beyond the fixed cost (for rent, utilities, and insurance) of $\$ 220$ per day, it costs $\$ 2.75$ for enough materials (flour, sugar, etc.) and labor to produce each dozen doughnuts. If the daily profit varies between $\$ 60$ and $\$ 270,$ between what levels (in dozens) do the daily sales vary?