State how each of the following would affect the average wage of college professors relative to other professionals in the long run. In each case, illustrate with a supply and demand model
a) Requirements to become a college professor increase from 1 PhD to 2 PhD's
b) Urban colleges around the country relocate to rural areas
c) The college-age population decreases.
d) The number of courses college professors have to teach each year is reduced by 25%.