Economists observed the only five residents of a very small economy and estimated each one's consumer spending at various levels of current disposable income. The accompanying table shows each resident's consumer spending at three income levels. Individual consumer spending by Individual Current disposable income $0 $20,000 $40,000 Andre 1,000 $15,000 29,000 Barbara 2,500 12,500 22,500 Casey 2,000 20,000 38,000 Declan 5,000 17,000 29,000 Elena 4,000 19,000 34,000 a) What is each resident's consumption function? What is the marginal propensity to consumer for each resident? b) what is the economy's aggregate consumption function? What is the marginal propensity to consume for the economic?