It takes 120 mL of 0.15 M of carbonic acid (H2CO3) to neutralize 300 mL of sodium hydroxide (NaOH) for the following balanced chemical reaction:

2NaOH + H2CO3 → N2CO3 + 2NaOH

The concentration of the sodium hydroxide _____.

0.03 M
0.24 M
0.12 M
0.06 M