Work = (force on the electron) times (distance the electron is moved).
Can you calculate the force on the electron ?
Sure ! It's pushing against a force of 180 Newtons per Coulomb,
and you know the charge on it.
Do you know the distance it's moved ?
Sure ! That's the 2.5 cm (=0.025 meter) between the plates.
Look at this:
Work = (force) x (distance)
= (180 N/C) x (1.602 x 10⁻¹⁹ C) x (0.025 m)
I get 7.209 x 10⁻¹⁹ N-m. (joules) Try it and see if you agree.
