JEE Main 2023 Chemistry question

20 mL of calcium hydroxide was consumed when it was reacted with 10 mL of unknown solution of . Also 20 mL standard solution of 0.5 M HCl containing 2 drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of 35.5 mL whereas the burette showed 25.5 mL initially. The concentration of is M. (Nearest integer)