1 coulomb of electric charge is carried by 6.25 x 10^18 electrons
1 Ampere = 1 coulomb per second
10 A = 10 coulombs per second
(2.0 x 10^20 electrons) x (coul / 6.25 x 10^18 electrons) / (10 coul/sec) =
(2.0 x 10^20) / (6.25 x 10^18 x 10) sec = 3.2 seconds