The following model was fitted to a sample of 60 families in order to explain household milk consumption: y1 = a+ BiXu+ BzXzi+ u where y:= milk consumption, in litres per week Xi = weekly family income, in hundreds of dollars X2 = family size. Part of the estimation results are as follows: Observations 60 Sum of Squared Residual 88.2 Total Sum of Square 162.1 Coefficients Standard Error Intercept -0.025 0.0 X1 0.052 0.023 X2 1.14 0.35 a) Write down the Sample Regression Function (SRF) in an equation form and interpret each of the estimated coefficients