1chem Q

One of the domestic drain cleaner sold in supermarkets named
'BUBBLES' contains concentrated sulphuric acid as the active
ingredient. A teacher carried out the following experiment to
determine the concentration of sulphuric acid in 'BUBBLES'.

a. 1 cm^3 of 'BUBBLES' was dilute to 250cm^3
with distalled water. 25cm^3 of the diluted solution were
measured and transferred to conical flask.The solution was
titrated against 0.2M sodium hydroxide solution. 18.1cm^3 of
the sodium hydroxide solution is required to complete the
reaction.calculate the concentration of sulphuric acid.

Please teach me!!