total cash op costs

PNA state in their investor presentation that the total cash operation cost for the Phu Kham Copper Gold Project is 74 cents lb with gold and silver credits at $450 and $8 (US). They further provide an annual cash flow scenario showing 3 options.

In option 3 they state that if the price of copper is $2.25lb and gold is $550/oz then the annual cash flow is $108 million and payback of the cost of the mine is less than 3 years.

Obviously I am not reading/interpreting the information correctly because even at $2.25 lb for copper and allowing .74 cent lb total cash cost I get a far greater profit figure than the one supplied.

ie 52T tons copper
2240 lbs per ton
Equals 116.5 million lbs of cu
At $2.25 lb minus .74 cents, Total
Cash Cost leaves $1.51 cents profit per
lb

This equals $175.91 mil

Where am I going wrong

TIA