If you were writing a fairly formal letter, and starting with the sentence, "You will not be expected to reply until after you have received your official letter from the Graduate School," and then wanted to go back to add an "of course," where would you put it?
The easiest place is at the beginning ("Of course, you will not--"). Another option is to put it at the end ("--letter from the Graduate School, of course.") There's also "You will not, of course, be expected--" and "You will, of course, not be expected--"
Which of these would you consider optimal? Which, if any, inappropriate?
(I have - obviously - just finished writing such a letter, and suddenly found myself wondering about how my choice would compare with others.)