Well, at the beginning we said we don't have any of the Y, our Y or concentration of our product is zero. And that means since this guy is zero for the reverse reaction, that means our rate going backwards is zero. And that makes sense because if none of the Y has formed yet, that means none of the Y can convert back to X. So let's go to this point somewhere in between our initial and our final. Well, somewhere here, our rate begins to decrease going this way. In other words, because our concentration of X begins to slowly diminish, this guy begins to get smaller.