2. (20 points) The following model is a simplified version of the multiple regression model used by Biddle and Hamermesh (1990) to study the tradeoff between time spent sleeping and working and to look at other factors affecting sleep: sleep = Bo + B totwrk + Bzeduc + Bzage +u, where sleep and toturk (total work) are measured in minutes per week and educ and age are measured in years. The estimated equation is sleep = 3638.25 0.148 * totwrk 11.13 * educ + 2.20 * age (112.28) (0.017) (5.88) (1.45) n=94, R2 = 0.127 (i) (8 points) Is either educ or age individually significant at the 10% level against a two-sided alternative? Show your work. (ii) (6 points) Dropping educ and age from the equation gives sleep = 3586.38 0.151 * toturk (38.91) (0.017) n=94, R2 = 0.115 Are educ and age jointly significant in the original equation at the 5% level? Justify your answer. (iii) (6 points) Does including educ and age in the model greatly affect the estimated tradeoff between sleeping and working