Calculate basicity

04年HKCEE chem (7)
7. An experiment, consisting of the three stages listed below, was carried out to determine the basicity of a solid acid : Stage 1: 1.15 g of a sample of the acid was weighed. Stage 2: The sample of acid was dissolved in some distilled water and then made up to 250.0 cm3 with distilled water. Stage 3: 25.0 cm3 of the solution obtained in Stage 2 was titrated against 0.100 M sodium hydroxide solution using phenolphthalein as indicator. 25.7 cm3 of the sodium hydroxide solution was required to reach the end point.(a) Briefly describe how the 250.0 cm3 solution was made up in Stage 2. (b) State the colour change at the end point of the titration in Stage 3. (c) (i) Calculate the number of moles of sodium hydroxide used in the titration.
(ii) Given that the molar mass of the solid acid is 90.0 g , calculate its basicity.

(8 marks)

I have done a,b and c(i), but not c(ii).
So, may you just simply give the answers of a,b and c(i) ?
For c(ii), may you show all the steps for the calculation ?

That's all, THX~~~