How far apart must be a proton from a group of 23 protons (held in place next to one another) if the magnitude of the electrostatic force acting on the lone proton due to the group is equal to the magnitude of the gravitational force on the lone proton at Earth's surface?

How far apart must be a proton from a group of 23 protons (held in place next to one another) if the magnitude of the electrostatic force acting on the lone proton clue to the group is equal to the magnitude of the gravitational force on the lone proton at Earth's surface? Number I Units V