1. The heart data set on D2L consists of a retrospective sample of males in a heart-disease high-risk 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 find the best poly- nomial model (b) Fit a cubic spline with three knots, the knots are chosen uniformly. (c) Fit a natural spline with same knots