chemistry
posted by grant .
Bornite (Cu3FeS3) is a copper ore used in the production of copper. When heated, the following reaction occurs.
2 Cu3FeS3(s) + 7 O2(g) 6 Cu(s) + 2 FeO(s) + 6 SO2(g)
If 3.88 metric tons of bornite is reacted with excess O2 and the process has an 75.6% yield of copper, what mass of copper,in metric tons, is produced?

figure out how many moles of bornite one has in 3.88 metric tons. Then you get 3 times as much Cu (theoritical yield), so multiply that by .756
That is the standard way.
An easier way is to figure how much copper is in the bornite, and multiply that by the yield (.756)
fraction copper= 3atomicmassCu/molmassBornite. 
help me with the answer ?