What normality of a solution that contains 280 grams of NaOH in 2000 ml of solution?

Equivalent mass of NaOH = 23.0 + 16.0 + 1.0 = 40.0
No. of equivalents of NaOH = 280 / 40.0 = 7
Normality of NaOH solution = 7 / (2000/1000) N = 3.5 N