According to Card (2009), (a) workers with less than a high school education are perfect substitutes for those with a high school education, (b) “high school equivalent” and “ college equivalent” workers are imperfect substitutes, and (c) within education groups, immigrants and natives are imperfect substitutes. For each of these comparisons, draw the isoquants for a production function that uses two types of workers. For example, in part (a), production is a function of workers with a high school diploma and workers with less education.