It did say that it was a "trick question".
I would suggest that the guy drinking is actually the bigger threat to life since he is actively driving about a 21,000,000 grain bullet. The guy with the gun out the window is dumb to be sure, but until he actually points it at someone and pulls the trigger, hes not much of a danger unless he drops it out the window at 60 MPH.
Remember, 1 pound = 7000 grains
Which is more of a danger...
a 2000 - 4000 pound car?
a 100 to 230 grain bullet?
Not a tough question to answer really.