You need to find out the maximum NPV of a hypothetical iron ore open pit as shown below. The iron ore grade is 72% and recovery is 90%. The market price of iron ore is $100/ton. The ore and waste block size are 30 by 30 by 30 m³ and annul production of six blocks (mining + stripping) is there. The mining cost is $35/ton and the stripping cost is $25/ton. The density for the ore and waste is 4.5 ton/m³ and 2.5 ton/m³ respectively. Assuming initial investment $50 million the interest rate is 5% per year.

W = waste; O = ore.