A model fit predicting preference for U.S. President (Democrat, Republican, Independent) using x = annual income (in $10,000) is log(π̂_D/π̂₁) = 3.3 – 0.2x and log(π̂_R/π̂₁) = 1.0 + 0.3x.

a. Find the prediction equation for log(π̂_R/π̂_D) and interpret the slope. For what range of x is π̂_R > π̂_D?

b. Find the prediction equation for π̂₁.

c. Plot π̂_D, π̂₁, and π̂_R for x between 0 and 10, and interpret.