An electronic instrument of mass $10 \mathrm{~kg}$ is mounted on an isolation pad. If the base of the isolation pad is subjected to a shock in the form of a step velocity of $10 \mathrm{~mm} / \mathrm{s},$ find the stiffness of the isolation pad if the maximum permissible values of deflection and acceleration of the instrument are specified as $10 \mathrm{~mm}$ and $20 g$, respectively.