How much work would be required to move an electron from 0.0529 * 10^-9 m from a proton to four times that distance?

Question

Quizplus · Accepted Answer

The work required to move an electron is given by the formula: 
Work = (charge of proton * charge of electron) / (4*pi*epsilon_0 * distance)
where charge of proton and electron are opposite in sign but equal in magnitude (1.602*10^-19 C) and epsilon_0 is the permittivity of free space (8.85*10^-12 C^2/(N*m^2)). 
So the work required to move an electron from 0.0529 nm to 4 times that distance (0.0529*4=0.2116 nm) is:
Work = [(1.602*10^-19 C)^2] / [4*pi*(8.85*10^-12 C^2/(N*m^2))*(0.2116*10^-9 m - 0.0529*10^-9 m)]
= 3.3*10^-18 J
This matches option B.

How Much Work Would Be Required to Move an Electron