It is isn't good to use the local units like Mana , Pathi etc in international measurement. why?​

because they are not standard unit(accepted globally)

Explanation:

hope its help

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach