An economist for the federal government is attempting to produce a better measure of poverty than is currently in use. To help acquire information, she recorded the annual household income, in thousands of dollars, and the amount of money spent on food during one week for a random sample of households. Below are four equations that were estimated by the economist with the data where x is the annual income (in $1,000) and y is the weekly food expenditure for the household. y = 153.90 + 1.96x Iny = 3.91 + 0.41 In x y =-172.34 + 108.81 In x Iny = 5.15 + 0.007x (a) In Excel, in one graph, plot each of the functions for x = 40 to x = 80. (b) Calculate the slope of each function at x = 60. State the interpretation of the slope. (c) Calculate the elasticity of each function at x = 60 and give its inter- pretation