Problem 3 (15 points) A mass spectrometer accelerates doubly ionized atoms of charge 2e over a potential difference V before they enter a uniform magnetic field B which is perpendicular to the direction of motion of the ions. If d is the radius of the ions' path in the magnetic field, what is the mass M of one ion? Express your answer ONLY in terms of V, B, e and d. The potential V is low enough that no relativistic corrections are needed