A current of 200 mA is flowing through the lamp. One ampere is the current that flows through the lamp when one coulomb of charge passes in one second. The charge of an electron is 1.602*10^-19 C.
The number of electrons that pass through the lamp in one second is equal to `(200*10^-3)/(1.602*10^-19)` . The number of electrons that pass through the lamp in one minute is equal to `(200*10^-3*60)/(1.602*10^-19)` = `7.49*10^19` .
Another way of determining this is to use the fact that one ampere is current that flows when `6.241*10^18` electrons pass through in one second. This gives the number of electrons passing through the lamp in a minute as `6.241*10^18*60 = 7.48*10^19`