If all the objects are placed at the same angle so all the light from the flashlight shine comes back to the flashlight. If the A object is placed at the specific location at which the mirror X reflects the light after hitting it, then the other E object is placed at the location where the light comes after reflecting the A object then the light comes back to the flashlight if the angle between objects placement is right.
It is rinsed one last time with the solution to be measured because if there is water in the burret, then it could alter the results. Slightly, but it is still altering it.
