He has a really tricky quiz. Let’s look at the forward motion again. Say I changed the last measurement from two down to one. You might remember the robot poses, we minus three, two and five. Before their modification, then my position was seven. But if one doesn’t really add up, a one suggests I might be at a different distance to the seven than the five over here that come from this side. So, here’s my quiz. First, I want you to know if I make this modification, what is the effect on x2? Will the estimate be smaller than five as we shrink the robot path a little bit? Will be exactly equals five like before or will be larger than five? Also want to know what’s the effect on x0. Will it be smaller than minus three, equal to minus three, or larger than minus three? This is a completely nontrivial quiz, it takes really some thinking. Invest in thinking and you can even go back and try it out.