The following assay data was collected from a copper$-$zinc concentrator:

Mass flow measurement showed that $2\mathrm{.}6\%$ of the feed weight reported to the copper concentrate, and $3\mathrm{.}5\%$ to the zinc concentrate. Calculate the overall economic efficiency under the following simplified smelter terms:

Copper: Copper price: $1000/$t

Smelter payment: $90\%$ of Cu content

Smelter treatment charge: $30/$t of concentrate

Transport cost: $20/$t of concentrate

Zinc: Zinc price:$400/$t

Smelter payment: $85\%$ of zinc content

Smelter treatment charge: $100/$t of concentrate

Transport cost: $20/$t of concentrate