Can you help me to solve this model.

1. In a study relating college grade point average to time spent in various activities, you dis- tribute a survey to several students. The students are asked how many hours they spend each week in four activities: studying, sleeping, working, and leisure. Any activity is put into one of the four categories, so that for each student, the sum of hours in the four activities must be 168. (a) in the model GPA = 50 + ,81study + zsleep + gwork + 4leisure + 1:. does it make sense to hold sleep, work, and leisure xed, while changing study? (b) Which assumption this model violates (assume a is uncorrelated with the independent variables)? (c) How could you reformulate the model so that its parameters have a useful interpretation and it satises the assumption you identied in the previous part