QuickStop provides its customers with coffee and donuts at 6:00 a.m. each day. The convenience store buys the donuts for 7 cents apiece and sells them for 25 cents apiece until 8:00 a.m. After 8:00 a.m., the donuts sell for 5 cents apiece. The number of customers buying donuts between 6:00 and 8:00 is uniformly distributed between 30 and 50. Each customer usually orders 3 donuts with coffee. Using continuous approximation, how many dozen donuts should QuickStop stock every morning to maximize revenues?