Can you solve this problem of effortlessly increasing worker productivity?

I swiped this problem from the book,The Art of Thinking Clearly by Rolf Dobelli. There are 6 car salespersons. Person 1 sells one car a week, person 2 sells 2 cars a week, and so on up to person 6 selling 6 cars per week. People 1 to 3 are in Department A and the rest are in Department B.

It is not hard to see that the average sales per person in Department A is 2 cars per week per person and in Department B it is 5 cars per week per person. Do you see a way of moving a person from one department to the other which will cause average sales per person to increase in both departments?

This phenomenon is known as the Will Rogers effect, because he once said that moving people form Oklahoma to California would increase the intelligence in both states.