A metallic solid sphere is placed in an uniform electric field. The lines of force follow the paths shown in figure.

Four equal charges, each $+\mathrm{q}$ are placed on the four corners of a square of side $a$. Then the Coulomb force experienced by one charge due to the rest of three is:

$\left(\mathrm{k}=\frac{1}{4\mathrm{\pi }{\mathrm{\epsilon }}_0}\right)$

Four charges of $+6\times {10}^{-8}C$ each are placed at the corners of a square whose sides are $3 \mathrm{cm}$, each. Calculate the resultant force on each charge and show direction in a diagram drawn to scale.