The heart data set consists of a retrospective sample of males in a heartdisease highrisk region of the Western Cape, South Africa. Use sbp (symbolic blood pressure} as response variable and obesity as predictor. (a) Fit a polynomial regression for the heart data set, use cross validation to nd the best poly nornial model (b) Fit a cubic spline with three knots, the knots are chosen uniformly. {c} Fit a natural spline with same knots