In a titration, $20.0{cm}^3$ of sodium hydroxide solution, $NaOH$, is titrated with $0.150{mol/dm}^3$ sulfuric acid, $H_2{SO}_4$. $2NaOH+H_2{SO}_4\to {Na}_2{SO}_4+2H_{2}O$ It is found that $18.40{cm}^3$ of sulfuric acid is required to completely neutralise the $20.0{cm}^3$ of the sodium hydroxide solution. Calculate the concentration of the sodium hydroxide solution in ${mol/dm}^3$. Give your answer to three significant figures.