Two small spheres, with charges 1 . 6 1 . 6 x 1 0 - 5 C and 6 . 4 6 . 4

 Two small spheres, with charges $1\mathrm{.}6$x$10$C and $6\mathrm{.}4$x$10$^-5 C$,$ are $2\mathrm{.}0$m apart. The charges have the same sign. Where, relative to these two spheres, should a third sphere, of opposite charge $3\mathrm{.}0$x$10$⁶ C$,$ be placed if the third sphere is to experience no net electrical force? Do we really need to know the charge or sign of the third object?