FIND

1 lb =453.59 g

125 lb of CuFeS₂= 125 x 453.59=56698.75 g CuFeS₂

Molecular weight of CuFeS₂ =184 g

If 184 g CuFeS₂  contains 64 g Cu

Therefore 56697.5 g CuFeS₂ should contain 19721.30 g Cu

Now 128 g Cu is present in 160 g Cu₂S

Therefore 19721.30 g Cu is present in 24651..625 g Cu₂S which is 54.34 lb of Cu₂S