The population of Champaign, Illinois is given for three years in the table below:

Year Population
1970 163488
1980 168392
2012 203276

(a)Using 1970 as t=0, create a linear model
from the first two data points in this table to
predict the population, p, as a function of the
number of years since 1970, t.

(b) If this model is used to predict the population of Champaign in the year 2012, will the model over estimate or underestimate the actual population? Explain.