Hi, First of all I did not create this question, but let's try to solve it together. Please see slides 33 if the lecture. The number of tuples in the resulting relation (after cartesian product is applied) are number of tuples in the first relation \times number of tuples in the second relation. In this case it should be 3 x 4 = 12. Also note for a simple cross product duplicates do not matter. But that answer is not there in the list. Perhaps the question is ambigious and may require filtering the tuples based on the common attributes which in this case is A. So in the 12 tuples that you get, filter out where R.A = T.A . You will only be left with 4. However, if you are doing that then it will be a join and should have a join operator / where condition, ref: slide 35. ANONYMOUS wrote: