Copper ore containing 80 wt.% inert solids, 12 wt.% CuSO4 and 8 wt.% water is to be extracted in a counter-current stage extractor to recover CuSO4 using pure water. After each stage, 1 ton of inert solids retain 2.5 tons of liquid (CuSO4 and water solution). Equilibrium is attained in each stage, and a basis of 100 tons/hr the copper ore can be used. If the strong solution produced is to consist of 0.12 mass fraction of CuSO4. The fractional recovery of CuSO4 from the ore is 0.95, what is the number of ideal stages required for the process? (round to one