I am studying the Art of Electronics and cannot follow the calculation steps regarding the resistors R in the attached image. Below the circuit, it is also described how the values for the resistors are determined. But what I don't understand is how R can be calculated by dividing the 6.5V by the base current. Isn't there also a certain amount of current flowing through the diode? I would say that the 6.5V should be divided by the sum of the diode current and the base current. What am I missing?