Need help with these questions please

[15pts] Consider a weighted simple linear regression model Yi = Bo + BIXi tei, for i = 1, ..., n, where Xi E R and conditional on X's, et's are independent normal random variables with mean 0 and variance o2 /wi. The values of {wi : i = 1, . .. , n} are known. (Note: please clearly define new notations if needed, and show all the derivation steps for the following questions) (a) [5 pts] Derive the specific forms of the Weighted Least Square (WLS) estimators of Bo and B1. (b) [5 pts] Under the WLS, what is the estimator of o2? Derive the expectation of the estimator. (c) [5 pts] Under the WLS, derive the form of the standard error of the WLS estimator B1