The answer is d because when you look at where the line starts, it is directly between 800 and 1200, therefore the y-intercept is 1000 and you can eliminate a and c. You can then infer that due to it being 1000 at 0 cars sold, they get 1000 per month and they get 150(inferred and/or calculated slope) per car they sell, therefore d is the answer.
