Hello. Suppose you were to assemble a sphere of negative charges. When you are done, the rest mass of the sphere is larger than that of the negative charges because they gain energy in forming the sphere. But the invariant mass of the electrons can't change and apparently gaining energy doesn't increase their mass but their inertia. So does the concept of mass defect still hold without relativistic mass? And does the sphere have higher invariant mass than the sum of the invariant masses of the electrons? Thank you.