The voltage across a lead-ion indicator electrode and a silver-silver chloride reference electrode immersed in 2.50X10-3 M Pb(NO3)2 at pH 4.0 was 0.278 V. If k(Cd2+/Pb2+) is 0.31. calculate the absolute and relative error in terms of the concentration of Pb2+ when the electrodes are used to measure the lead-ion concentration in a solution containing 3.17X10-2 M Pb(NO3)2 and 8.03X10-3 M Cd(NO3)2