The result suggests that, for every $1 increase in State expenditure per pupil on public schools, a public school teacher's average salary goes up by about $3.29. Further, for a state in the North region, the mean salary of the teachers is lower than that of West region by about $1673 and for a state in the South region, the mean salary of teachers is lower than that of the West region by about $1144. Figure 3 depicts this model diagrammatically. The average salary lines are parallel to each other by the assumption of the model that the coefficient of expenditure does not vary by state. The trade off shown separately in the graph for each category is between the two quantitative variables: public school teachers' salaries (Y) in relation to State expenditure per pupil on public schools (X).