PLEASE EXPLAIN WITH "R" CODES AND AN EXPLANATION

Use the data set ColGPA.x/sx for this exercise. a) Use OLS to estimate a model relating colGPA to hsGPA, ACT, skipped, and PC to obtain the OLS residuals ei. What does a White's test for heteroskedasticity show? b) Now regress ei2 on the fitted values of colGPA and colGPA 2 and save the fitted ei2 as hi to obtain a feasible weighted least squares estimates using the weights I/hi. Compare the weighted least squares estimates for the effect of skipping lectures and the effect of PC ownership with the corresponding OLS estimates. (Compare both coefficient values and their std. errors/significances.) c) For both the OLS and the WLS estimations, obtain heteroskedasticity-robust standard errors. Do you find significant changes from part (b)