Help me with calculation and explanation

The World Health Organization says that it is too costly to try to fully eradicate malaria. By using nets, medicine, and DDT it is possible to eliminate 90 percent of malaria cases. But to eliminate 100 percent of cases would be extremely costly. Describe how the opportunity cost of controlling malaria changes as more resources are used to reduce the number of malaria cases. Other goods and services (millions of units per year) PPF data Malaria control (percent Other goods and services of cases eliminated) (millions of units per year) 5 10 5.5 20 5.4 .... 30 5.3 40 5.2 50 5.1 60 5.0 70 4.8 80 4.1 90 3.1 0 10 20 30 40 50 60 70 80 90 100 100 O Malaria control (percent of cases eliminated) Alt Text: PPF