A p-type Si is doped with NA acceptors close to the valence band edge. A certain type of donor impurity whose energy level is located at the intrinsic level is to be added to the semiconductor to obtain perfect compensation. If we assume that simple Fermi-level statistics apply, what is the concentration of donors required? Furthermore, after adding the donor impurity, what is the total number of ionized impurities if the above sample is perfect compensation?