One box is 120g.
mass of 126 boxes = 126*120 = 15120 g
(note: used an additional significant figure when first digit is a 1, so four significant figures)
Using the conversion 1 lb. = 453.6 g/lb
15120g = 15120 g / (453.6 g/lb) = 15120 g * (1/453.6) lb/g = 33.3 lbs. (3 significant figures)
