11. Complete the Table below, assuming a profit allowance of $4.50 per tonne. Then, assuming a stripping cost of $7.25 per tonne of waste and a copper price of $3.20 /lb, calculate the economic stripping ratio (SR_e) for each of the copper head grades. Also, calculate the cutoff grade for copper prices of $3.50/ lb and $2.69/ lb. Show your calculations. -- Note: Head grade is a general term referring to the grade of ore delivered to the processing plant. Since the broken ore comes from various sections of a mine, the ore accepted at the Mill/Processing plant consists of a blend of various ore grades. Therefore, the term head grade or simply head is commonly used in the plural form, i.e. head grades or heads. (18 points)

Heads % Cu	2.3	2.1	1.7	1.5	1.4	1.2
% Rec'd	92.5	89	82	79	72	66
Rec'd Cu (Kg/tonne)
Value of Ore ($/tonne)
Costs ($/tonne)
Mining	13.10	13.10	13.10	13.10	13.10	13.10
Milling	19.05	19.75	21.35	22.05	23.50	25.35
Others (Depr, etc.)	12.30	12.30	12.30	12.30	12.30	12.30
Total Prod. Costs ($/tonne)
Profit Allowance ($/tonne)
Total Cost ($/tonne)
Net Value ($/tonne)
Stripping Costs ($/tonne)
Economic Strip ratio