A system consists of electrons, protons, and neutrons. it contains 250 neutrons and 150 protons.
me = 9.11 x 10⁻³¹ kg
mp = 1.673 x 10⁻²⁷ kg
mn = 1.675 x 10⁻²⁷ kg.
if the total charge of the system is -35 e , what is its mass?