Calculate in the given figure: work done in taking the same amount of negative charge from $A$ to $B$, $(OA = 0.10 m, OB = 0.20 m)$.

       

A charge $\mathrm{A}$ of $8.0 \mathrm{\mu C}$ is situated at a distance of $1.00$ metre from a charge $\mathrm{B}$ of $-2.0 \mathrm{\mu C}$, as shown. Calculate the potential at the mid-point $\mathrm{C}$ between $\mathrm{A}$ and $\mathrm{B}$.  Also calculate the potential at $\mathrm{D}$ which is at a distance of $0.80 \mathrm{m}$ from $\mathrm{A}$ and $0.20 \mathrm{m}$ from $\mathrm{B}$. How much work will be done in taking $0.02 \mathrm{\mu C}$ of charge from $\mathrm{D}$ to $\mathrm{C}$?