Acopper ore containing 4.3 wt% water, 10.3 wt% cuso, and 85.3 wt% rock is fed to a staged counter current extractor at a rate of 11.7 tons per hour. we wish to recover 98% of the copper sulfate using pure water as the fresh solvent. the solution produced is to be 10 wt% copper sulfate and 90 wt% water. if after each stage 1 ton of inert rock retains 2 tons of water plus the dissolved copper sulfate, how many stages are required?