56. Solving a chemistry problem

283. To determine SO3 in cement, a sample of cement weighing m (g) was dissolved, filtered, and the solution was passed through a chromatographic column containing a cation exchanger in the H-form. The eluate and washings were collected in a 100 ml volumetric flask and made up to the mark with water. Then 25 ml of the resulting solution was titrated potentiometrically on an autotitrator with 0.1 M NaOH solution and the following results were obtained:
task number 283
m, g 1.0012
V(NaOH), ml 0.90
Determine the percentage of SO3 in the cement.