What is the mass range for the potassium hydrogen phthalate necessary to obtain 25 ml titre of 0.15 M NaOH

This is for my chem lab tommorrow! I have no idea how to work this out, please help??

Mol NaOH in 25mL of 0.15M NaOH solution = 25/1000*0.15 = 0.00375 mol NaOH
NaOH reacts in 1:1 molar ratio with KHP.
Therefore you need 0.00375 mol KHP
Molar mass KHP = 204.22 g / mol
0.00375 mol = 0.00375*204.22 = 0.766g KHP required.
You should therefore weigh out between 0.700 and 0.840 g = which gives you 10% on either side. Your titre should then be between 22.5 and 27.5 mL.