A student writes about problem set 6:

     Sorry to bother you again Dr. Patt,

     I was looking through the course website
     and I noticed that there was a problem
     set 6 posted. It says that the problem
     set is "optional" and "not due". Could
     you please explain what you mean by optional
     (as in, you don't care whether we
     turn it in or not, if it
     takes the grade of the lowest problem set--maybe being
     a little too optimistic here, or whatever
     the case may be). Could you please
     clarify this doubt that I have?

     Thanks, and sorry again for what may seem like a stupid question,
     << name withheld to protect the too optimistic student >>

"Optional" means: you can do it if you want to.
"Not due" means: there is no due date. i.e., you don't turn it in.

Then why would we possibility go to the trouble of making up another problem set? Hint: working problems is one good way to test your understanding of concepts. Hint 2: There is one more test of your ability to master concepts still on the horizon.

Yale Patt