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Blame Greg Biffle's disappointing start to the season mostly on misfortune, but don't be surprised if Biffle and the No. 16 Ford of Roush Racing qualify for the Chase for the Championship, writes Benny Parsons of NBCSports.com.

Q: Rumor has it that Dale Earnhardt Jr. will drive the No. 3 car after he wins a Cup title for Dale Earnhardt Inc. Is there any truth to this, and would you agree that only Earnhardt should ever be allowed to drive the No. 3 car?
— Chuck Royal, Martinsburg, W. Va.

A: At some point in the future, if Junior desires to drive the No. 3 car that his late father drove during his Cup career, I feel NASCAR should allow him to do so. But I don't know why he would want to take the seat in the No. 3 car.

I think in his racing career Junior has done a very admirable job of being his own man. He has not gone out and tried to emulate his father by way of bumping other drivers and their cars while racing. Junior has been a very clean racer, and a credit to the sport.

I know why so many want to see him switch over and drive the No. 3 car -- it's because they want to see that car back racing with an Earnhardt in it. But to me if Junior does make the switch, it's a no-win situation for him.

By getting behind the wheel of the No. 3 car, Junior invites even more comparisons to his father. I applaud the way Junior has taken the No. 8 car and done a great job with it. It may not be as famous as the No. 3 car, but the No. 8 is Junior's number, and that's his identity.

By the way, NASCAR owns the numbers to cars, and it issues numbers to the teams. Owners have the option of not using a number for one year, but after that they have to use the number or lose it back to NASCAR.

Since Dale Earnhardt's death in 2001, Richard Childress Racing, which the late Earnhardt drove for, has not used the No. 3, so it's back with NASCAR, but don't expect it to ever be issued to anyone else except Junior.

Q: After getting a very good look at the underside of Tony Stewart's Busch car during a recent race, I was wondering how much attention is given to the aerodynamics of the underside of these cars?
— Dennis Pugsley, Renton Wash.

A: There is attention spent on the aerodynamics on the underside of a car, but there's so little that can be done under the car as far as aerodynamics is concerned, that it's not a point of heavy emphasis.  

When it comes to aerodynamics on a car, the key is the front air dam, which is a metal strip that is located beneath the front grill and under the bumper. It is usually just inches from the track surface, and its purpose is to provide aerodynamic downforce at the front end of the car.

Teams want to get the front air dam as close to the ground as they can so there will be very little air going under the car when it is racing. This -- and not the underneath of the car -- is where aerodynamics is most important, and can most affect a car's performance in a race.

Q: What percentage of the race purse goes to the drivers?
— Cooke, North Port, Fla.

A: There is no standard policy since the teams are independent contractors so agreements vary among them.

The owner and driver have worked out beforehand an agreement on how the money earned by the car in the race will be divided. These agreements usually have a range of 25 to 50 percent of the money won going to the drivers if they win the race.

And if he places anywhere from second to last, there's another predetermined percentage the driver receives -- usually 40 percent of the purse for the better and more well-known drivers.

Drivers also reach agreements with owners on a guaranteed amount of money they will be paid against the percentage of their winnings. If their winnings fall short of the guaranteed amount, the owner pays the difference. If they exceed that amount, then there's a percentage spilt that takes place between driver and owner on any money earned over the amount guaranteed the driver.

Additionally some driver contracts contain assorted bonuses and perks based mostly on performance that can earn drivers additional money.