Chemistry help!!! urgent!!!!?

i need to find the theoretical yeild for my ignment. this experiment determines whether there is 6% of sulfur is present as sulfates in a sample of fertiliser. i am using 4 g of fertiliser along with 5 g of BaCl2. which produces a BaSO4 precipitate. my actual yeild is 4.49g. and from that i need to find out whether there is 6% of sulfur present as sulfates. if not can u show me how to get to it? thankyou