A doughnut shop sells a dozen doughnuts for $7.50. Beyond the fixed cost of $260 per day, it costs $3.25 for enough materials and labor to produce each dozen of doughnuts. During the month of January, the daily profit varies from a low of $318 to high of $607. Between what levels (in dozens of doughnuts) do the daily sales vary?

The daily sales vary between a low of ________ dozen doughnuts to a high of_______ dozen doughnuts.