Final Stages of Planet Formation

My lecture will address three major questions regarding solar system planets. What determined their number? Why are their orbits nearly circular and coplanar? How long did they take to form? Answers to these will be given in terms of: stability against large scale chaos; dynamical friction by small bodies; and the accretion rate at the geometrical cross section in the inner planet region and the ejection rate at the gravitationally enhanced cross section in the outer.