A student added solid Na₂O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was transferred to another volumetric flask and diluted to 500.0 mL. The pH of the diluted solution is 13.25. 

(a) What is the molar concentration of hydroxide ions in (i) the diluted solution, (ii) the original solution? 

(b) What mass of Na₂O was added to the first flask?