4. (1 Point) A common trick for evaluating multiple integrals that we've done many times throughout Chapter 15 is to split the multiple iterated integrals into a product of several single integrals. However, we must be careful to make sure that certain conditions are met for this to be a valid shortcut. Consider the following three equations - two of them are false, and one of them is true. Identify the valid line, and explain why separating is invalid in each of the other two cases. Give your explanation in a few clear, concise, complete sentences. 2. J. . cos (xy) dydr = ( / cos (x) dx ) (J. cos (y) dy ) 3. J J ex duda = (fedz) (S, du) The only valid line here is line O Line 1 O Line 2 O Line 3 because