Variables	Description
price		in X*1000 / acre
county		0=San Mateo 1=Santa Clara
size		acres
elevation	Average elevation in feet above the see level
sewer		Distance to the sewer connection
date		date of sale backward from now (month)
flood		flooding by tidal action=1 otherwise=2
distance	distance from current project

First model:    log(price) = b0 + b1 elevation + b2 date + b3 flood
			+b4 distance + e

Second model:   log(price) = b0 + b1 elevation + b2 date + b3 flood
		+b4 distance + b5 county + b6 (county*elevation) + e