How many hours a frame for Pixar's Cars?

You've got to be kidding me.

Answer: D. The average Cars frame took 15 hours, despite a 300x overall increase in compute power. The artists have an essentially infinite appetite for detail and realism, and Pixar's resources have grown over the decade so it can afford to allocate more computers to the task, allowing each to run longer to achieve the artist's and animator's ambitions for the scenes.

15 hours per frame. As a reference, Toy Story took two hours to render a frame. I guess we know why the movie looks so smooth, but it it really necessary when you're creating a animated movie? If we were expecting a realistic animated movie, I would understand but cars?
anywho...