Two plastic balls, each of radius $16\mathrm{.}0$ cm$,$ are placed so that there is a $25\mathrm{.}6$ cm space between them. The charge on one ball is $+4\mathrm{.}30$ nC and the charge on the other is $-2\mathrm{.}90$ nC$.$ What is the magnitude of the electric field at a point directly midway between the two balls?