Balanced equation is

a) 328 g calcium nitrate liberates 4 x 22.4 litres of NO2 [ \(\because\)4 moles of NO2 is formed ]
The amount of NO2 liberated from 16.4 g of calcium nitrate (4 x 22.4 x16.4)/328= 4.48 litres .
b) 328 g of calcium nitrate gives 112 g of CaO.
The amount of CaO obtained from 16.4 g of calcium nitrate = (112 x 16.4)/328 = 5.6 g.