The answer is liter hope this helped :)
It has 2 nitrogens. This is because there is 1 nitrogen in the ammonium, and there are two ammonium molecules.
Try 0.80 grams NaOH . M=mol/L if you rework it to get mol, you have mol=0.20M×0.100L which is 0.02mol of NaOH, multiply that by the amu of NaOH (39.998) and should get 0.799g