Here's the start to Exercise 4 in 12.5. As it turns out, we probably don't need to interpolate the data, but if we did need to do that, here's a nice way to do it.The function G is plotted below the definition.with(CurveFitting):G:=unapply(Spline([229,371,458,513,425,404,392],[39,81,82,79,84,85,84],x),x);plot(G(x),x=220..600);