When the n is so small that only an infinitesimal population
resides in the suburbs, then there is no suburban congestion and
no rent premium for residing in the core and O is zero since there
is no ADLR to redistribute. Then, dO/dn40 since dR 1 /dn40
as seen in Proposition 1. Thus, as the city grows spreading into
the suburbs, the rent premium in the core rises, and the public
component of income also grows by the redistribution of the
aggregate differential rent in the core.