Utilizing Figure 19.10 as a reference, approximate the amount of energy needed to extract and treat copper from ore with a grade of 3.0 percent. Then, perform the same calculation for ore with a grade of 0.3 percent, which is currently the minimum grade being mined.

Figure 19.10 The energy necessary to recover copper from its ores and by atomic substitution from common silicate minerals. (Reproduced with permission from R.B. Gordon, T.C. Koopmans, W.D. Nordhaus, and B.J. Skinner, Toward a New Iron Age? Cambridge, MA: Harvard University Press, 1987.)