The dataset bc, on breast cancer, is installed with STATA and can be retrieved by typing webuse be in the command window. The dataset has the following variables: age, smoking, dietfat, t, and dead where t is the time variable and dead is the event variable. To fit the stratified Cox proportional hazards model, the variable "dietfat was transformed as follows: diet 1, dietfat 5.6. (4.1) STATA code and output for fitting the Stratified Cox proportional hazards model are given below. xi: stcox age i.smoking, strata(diet) nolog i. smoking _Ismoking_0-1 (naturally coded; Ismoking_0 omitted) failure _d: dead analysis time _t: Stratified Cox regr. -- Breslow method for ties t Number of obs 80 No. of subjects = No. of failures = Time at risk 80 58 1257.07 LR chi2(2) Prob > chi2 151.47 0.0000 Log likelihood -87.086271 t | Haz. Ratio Std. Err. z P>z! [95% Conf. Interval] age 1 1.393104 3.616207 .0603696 1.326514 7.65 3.50 0.000 0.000 1.279667 1.762023 1.516596 7.421556 Ismoking_1 Stratified by diet estat ic Akaike's information criterion and Bayesian information criterion Model Obs 11 (null) 11 (model) df AIC BIC 1 80 -162.8237 -87.08627 2 178.1725 182.9366 Note: N=Obs used in calculating BIC; see [R] BIC note. (a) Interpret the point estimates of the hazard ratios and their 95% confidence intervals for the variables age and smoking, (b) Write down the fitted model. (2)