Charges 2

I didn't really learn anything new this past week about charges except for the fact that I have no idea how to do the review sheet. What i want to know is the answer to 6b.) on P.A. #31b, the one where it says: if there is about 13 pounds repulsive in each little helium than what is holding the nucleus together? Still clueless about some parts in this unit, hopefully everything is covered in today's review.