Again, start with the original model, but now allow wages to differ across four groups of people: a. married and black b. married and nonblack c. single and black, and single and nonblack. what is the estimated wage differential between married blacks and married nonblacks?

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.