Problem 3.6

A positive point charge \(50 \mu \mathrm{C}\) is located in the plane \(x y\) at the point with radius vector \(\mathrm{r}_ {0}=2 \mathbf{i}+3 \mathbf{j},\) where \(\mathbf{i}\) and \(\mathbf{j}\) are the unit vectors of the \(x\) and \(y\) axes. Find the vector of the electric field strength \(\mathbf{E}\) and its magnitude at the point with radius vector \(\mathbf{r}=8 \mathbf{i}-5 \mathbf{j} .\) Here \(r_{0}\) and \(r\) are expressed in metres.