N4

In dataset of a cross-section of cars advertised on an online platform, log price is regressed on a binary variable that is 1 if the ad comes from a dealer and 0 if it comes from the owner of the car. The slope coefficient is 0.1. When we add the age of the car to the regression, the slope coefficient on the same binary variable is 0.05. Interpret both numbers.

In the previous example the coefficient on the age of cars is -0.1. Are dealer-advertised cars older or younger on average? By how much?