Joe: "i think the key additional information you need to know in deciding whether the doctor should keep the medical practice open 9 hours per day rather than 8 hours is the amount of profit she is currently making while being open 8 hours. then she can compare the profit earned from being open 9 hours with the profit earned from being open 8 hours. this information is more important than the additional revenue and additional cost of being open 1 more hour."