An Elections Officer Wants to Model Voter Turnout $( y )$

An elections officer wants to model voter turnout $( y )$ in a precinct as a function of the type of precinct.
Consider the model relating mean voter turnout, $E ( y )$ , to precinct type:
$$\begin{array} { l l } E ( y ) = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } , \text { where } & x _ { 1 } = 1 \text { if urban, } 0 \text { if not } \\& x _ { 2 } = 1 \text { if suburban, } 0 \text { if not } \\& \text { (Base level = rural) }\end{array}$$
Interpret the value of $\beta _ { 2 }$ .

A) the difference between the mean voter turnout for suburban and rural precincts
B) the difference between the mean voter turnout for suburban and urban precincts
C) the mean voter turnout for suburban precincts
D) the rate of increase in voter turnout $( y )$ for suburban precincts, i.e., the slope of the $y - x _ { 2 }$ line