Two-point charges $+9\mathrm{q}$ and $+\mathrm{q}$ are kept $16 \mathrm{cm}$ apart. Where should a third charge $\mathrm{Q}$ be placed between them so that the system remains in equilibrium?

$\left(\frac{1}{4{\mathrm{\pi \epsilon }}_0}=9\times {10}^9 \mathrm{N} {\mathrm{m}}^2 {\mathrm{C}}^{-2}\right)$

A point charge $q_1$ exerts a force $F$ upon another point charge $q_2$. If a third charge $q_3$ be placed quite close to the charge $q_2$, then the force that charge $q_1$ exerts on the charge $q_2$ will be,