$\begin{align}  & \left| \Delta V \right|=Ed\Rightarrow 200=E\times 5\times {{10}^{-2}}\,\,\,\,\Rightarrow \,E=\frac{200}{5\times {{10}^{-2}}}=4000\frac{N}{C} \\  & {{W}_{E}}=-\left| q \right|Ed\cos \theta =-15\times {{10}^{-9}}\times 4\times {{10}^{3}}\times 2\times {{10}^{-2}}=-120\times {{10}^{-8}}=-1/2\mu J \\ \end{align}$