求救!维生素A 分子量是286.64,每个分子包含1个氧原子,问氧的百分数.3位有效数字.C = 12.01,

求救!维生素A 分子量是286.64,每个分子包含1个氧原子,问氧的百分数.3位有效数字.C = 12.01,
Vitamin A has a molecular weight of 286.64 and contains one oxygen atom per molecule.To three significant figures,what is percent of oxygen?
(Atomic weights:C = 12.01,O = 16.00,H = 1.008).