\( 20 \, \text{mL} \) of \( 2 \, \text{M} \) NaOH solution is added to \( 400 \, \text{mL} \) of \( 0.5 \, \text{M} \) NaOH solution. The final concentration of the solution is __________ \( \times 10^{-2} \, \text{M} \). (Nearest integer)