What are the correct SI units of electric field?

A displacement vector from a charge to a field point is $\overrightarrow{r}=(12\hat{i}-5\hat{j})$ $\text{cm}$ . What is the corresponding scalar distance $r$ in SI units?

At a point $P$, the electric-field contributions from several source elements are $E_x=-300$ $\text{N/C}$ and $E_y=400$ $\text{N/C}$. What are the magnitude and direction of the net field measured counterclockwise from the $+x$ axis?

A uniformly charged rod lies along the $x$-axis from $x=0$ to $x=L$ with linear charge density $\lambda$. At a point on the $x$-axis located at $x=a$, where $a>L$, which integral correctly gives the $x$-component of the electric field?

A semicircular arc of radius $R$ with uniform linear charge density lambda occupies the upper half of a circle centered at the origin. Which expression gives the net electric field at the center?