8. In the data "demog data.csv", if you model the "INCTOT" variable as a linear function of the "AGE" variable, what slope and intercept give the line with the least squares best fit? (You may use a built-in function for this or the formulas derived in class) (10 points) This question uses 2018 data primarily for Denver county accessed through IPUMS- USA, University of Minnesota, www.ipums.org , Steven Ruggles, Sarah Flood, Ronald Goeken, Josiah Grover, Erin Meyer, Jose Pacas and Matthew Sobek. IPUMS USA: Version 9.0 [dataset]. Minneapolis, MN: IPUMS, 2019. https://doi.org/10.18128/D010.V9.0 The PUMA-to-county restriction was done using MABLE, http://medc.missouri.edu/websas/geocorr12.html. The data are restricted to women in the age range 30-80 in PUMAs primarily in Denver. 9. Make a scatterplot with the "AGE" variable on the horizontal axis and the "INCTOT" variable on the vertical axis. Include the line computed in question 8. (If you used the built-in function for question 8, please extract the values of the slope and intercept from the fitted model object, rather than using copy-paste.) (10 points) 10. In the data set "demog data.csv" what is the mean value of INCTOT for women in each category of EDUC? (For full credit, please do this without looping through the EDUC values. You can use "summarize" from dplyr, with group_by.) (5 points) 11. Please restrict the data set "demog data.csv" to cases in which "INCTOT" is greater than 0 and "EDUC" is greater than 4. What is the mean value of "INCTOT" for the remaining observations? (5 points)