Study the diagram. an illustration of a transverse wave with the high point of the wave labeled a, the low point of the wave labeled c, the height of the wave was labeled b and the distance between two adjacent low points labeled d. point c identifies the of the wave.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.