At the center, 6 unmarked red balls are interspersed with 4 blue balls marked with plus signs. A green cloud with 2 concentric white lines surrounds the center, with 2 small green balls marked with minus signs on the inner white line and 2 small green balls marked with minus signs on the outer white line. What value is closest to the mass of the atom? 4 amu 6 amu 10 amu 14 amu