Titration calculations

A student titrates 25.0 cm³ of sodium hydroxide with 0.200 mol/dm³ hydrochloric acid. The end‑point is reached when 18.0 cm³ of the acid has been added. Assuming the reaction is $\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}$, what is the concentration of the sodium hydroxide solution?