Five points charges, $+q$ each is placed at the five vertices of a regular hexagon. The distance of the centre of the hexagon from any of the vertices is $a$. The electric field at the centre of the hexagon is

A ring of charge with radius $0.5 \mathrm{m}$ has $0.002 \pi \mathrm{m}$ gap. If the ring carries a charge of $+1 \mathrm{C}$, the electric field at the centre is

A point charge $\mathrm{q}=-8.0 \mathrm{nC}$ is located at the origin. The electric field (in ${\mathrm{NC}}^{-1}$) vector at the point $\mathrm{x}=1.2 \mathrm{m}, \mathrm{y}=-1.6 \mathrm{m}$, as shown in figure, is