An engineer used travel demand data for the year 2018 to estimate the pammeters of a shopping trip generation model. The parameters for trip productions 0, and trip attraction D, regression models are given in Tables 1 and 2. Table 1: Trip production Of regression model parameter estimates Variables Average family income in zone i Number of unemployed people R-square-0.83 Coefficient 0.35 -1.25 t-stats 4.02 -1.98 Table 2: Trip attraction D, regression model parameter estimates Variables Size of commercial floorspace in zone / Area of free parking space in zone R-square 0.83 Coefficient 0.45 0.55 t-stats 6.71 5.36 Using the information above, answer the following questions: (a) (5 marks) Justify the use of cach of the four explanatory variables in terms of the causal relationship they possess on their respective dependent variables O, and D/? (b) (4 marks) What does the t-stats values tell you about the estimated coefficients? (c) (6 marks) Given the information fisted in Table 2.3, predict the number of produced trips if the average family income will inerease by 5% and 10% for TAZS I and 2, respectively, in the period 2011 and 2031, while unemployment will remain constant over time. Table 3. Average family income in Unemployed people in 2011 2011 TAZ 65000 2000 2. 55000 2500