FIGURE D.1 Ingrid’s Utility FunctionThe three-dimensional hill shows how Ingrid’s total utility depends on her consumption of housing and restaurant meals. Point A corresponds to consumption of 3 rooms and 30 restaurant meals. That consumption bundle yields Ingrid 450 utils, corresponding to the height of the hill at point A. The lines running around the hill are contour lines, along which the height is constant. So point B and every other point along the same contour line as point A generates the same level of utility.