Charge on a cube

$3$ Eight point charges, each of magnitude $q=1\mathrm{.}9699999999999998$ e$-06C,$ are located on the corners of a cube of edge $s=28\mathrm{.}2cm,$ as shown in the figure. What is the magnitude of the resultant force exerted by the other charges on the charge located at point A$?$

$($Please answer in SI units and explain how to solve this question$)$