The Na+ concentration of a solution was determined by measurements with a sodium ion-selective electrode. The electrode system developed a potential of -0.2462 V when immersed in 10.0 mL of the solution of unknown concentration. After addition of 1.00 mL of 2.00 ( 10-2 M NaCl, the potential changed to 20.1994 V. Calculate the Na+ concentration of the original solution.