Kimberly Polecek, age 11, of Oklahoma City, Okla., for her question:

WHAT EXACTLY IS A CABOOSE?

You'll find a caboose at the end of every freight train. This very last car, often brightly colored, is the rolling home for the train's crew and is also the office for the conductor. Much of the paper work necessary to move a freight train across the country is handled at a desk in the train's caboose.

About 95 percent of the money earned by railroads in the United States comes from hauling freight. Each day as many as 10,000 freight trains travel to almost every section of the country, and most have a caboose to bring up the rear.

The average freight train has about 70 cars and one caboose, although some freight hauls unite 200 or more cars. The average train carries about 1,800 tons of merchandise.