A student in A.D.1997 learns about many exciting people and events in history and decides to visit them in a time machine. After firing up the machine, the adventure begins with a visit to the famous Greek philosopher Aristotle in 350 B.C. Following an interesting discussion with Aristotle about logic and ethics, the student then decides to see the effects of some of these teachings by witnessing Lincoln's Emancipation Proclamation in A.D.1863. After this comes a visit to the ancient civilization of Sumeria in 3500 B.C., where our intrepid traveler learns to make pottery and observes the characteristics of such an early civilization. The student then returns home to the present to refuel and to report on these amazing experiences (and to use the rest room, of course). Continuing the adventure, the time-traveling math lover makes a trip to see the young King Tut of ancient Egypt in 1340 B.C., where Tut explains the intricacies of the lengthy embalming process. Having witnessed the wealth and power of this ancient figure, the student decides to visit the powerful Mongol warrior and ruler, Genghis Khan, in A.D.1192. Genghis Khan gives a very interesting lesson in table manners and etiquette. Being absolutely exhausted (well wouldn't you be after sitting in a chair for thousands of years?), the student returns home and completes a report on the history of the world.

The time machine is fueled by uranium and requires 6 grams to make a time-shift, plus an additional 2.5 grams of uranium per year traveled. How much uranium did the student use?

And the answer is...