Classroom activity sheets: Please note that for any class room activity sheets for which solutions are not available here, you can write your solutions and submit them. That will give you extra credit. There is no time limit for this. Even if other students have submitted solutions, you can submit yours if yours point out some nice aspect previously neglected. Even if the solution was explained in class, do not hesitate expressing the same solution in your language -- it is very important! The extra credit points will be good for recovering from some lost points in homework etc.