Nonlinear regression using spline. (20 points.) The coefficient of thermal expansion y changes with temperature x. An experiment to relate y to a was done. Temperature was measured in degrees Kelvin. (The Kelvin temperature is the Celcius temperature plus 273.15). The raw data file is copper-new.txt 25 15 coefficient of thermal expansion 10 DO 0 0 00 0 000 O O 200 400 600 800 1000 temperature (a) (10 points) Perform linear regression on the data. Report the fitted model and the fitting error. (b) (10 points) Perform nonlinear regression with spline function (i.e., using all data points). Use cross validation for find A. Report the fitting error. Please write your own code. Predict the coefficient at 400 degree Kelvin, for both linear and non-linear regression models. Which one do you think is more accurate