Charges $\mathit{+}q$ and $\mathit{–}q$ are placed at $\mathrm{A}$ and $\mathrm{B}$ respectively which are at a distance $2L$ apart. If $\mathrm{C}$ is the midpoint between $\mathrm{A}$ and $\mathrm{B}$ then work done in moving $Q$ from $\mathrm{C}$ to $\mathrm{D}$ (through semicircular path $\mathrm{C}\mathrm{R}\mathrm{D}$ ) and from $\mathrm{C}$ to $\mathrm{\infty }$ are respectively