Refer to poverty_lines.xlsx for this question. The X-axis in the graph represents the average income of a country in US$ PPP per day. The Y-axis is also in US$ PPP per day. The lines recommend a poverty line for a country with a given average income according to three notions: 1) that national poverty lines should be absolute, 2) that they should be strongly relative, or 3) that they should be weakly relative, in Ravallion's terms