HW question- Millikan's oil drop experiment?

Question

A chemist in a galaxy far away performed the Millikan oil drop experiment and got the following results for the charge on various drops. What is the charge of the electron in zirkombs?

2.56*10^-12 zirkombs 7.68*10^-12 zirkombs

3.84*10^-12 zirkombs 5.12*10^-12 zirkombs

Answer 1

1.28*10^-28 zirkombs

"Knowing the electric field, the charge on the oil droplet could be determined. Repeating the experiment for many droplets, they found that the values measured were always multiples of the same number"

http://en.wikipedia.org/wiki/Millikan%27...

all of the zircombs given are multiples of 1.28e-12:

2.56*10^-12 zirkombs is 2 times 1.28e-12

3.84*10^-12 zirkombs is 3 times 1.28e-12

5.12*10^-12 zirkombs is 4 times 1.28e-12

7.68*10^-12 zirkombs is 6 times 1.28e-12