We construct a portfolio with four stocks: WMT (Walmart), BAC (Bank of America), XOM (Exxon), and PFE (Pfizer), with one constrant of LongOnly. Use R to complete this question. Please include the code you run in the Rstudio console and the results from the console.

(a) Use R to extract daily closing prices starting from 2018-10-30 of those four stocks from Yahoo!Finance and calculate portfolio returns. (b) Locate the Global Minimum Variance Portfolio (GMVP), i.e., make ggplot (bar) of the weights of the four assets within the GMVP. Find the 1-day 99% percentage VaR of the GMVP. (c) Locate the tangency portfolio, i.e., make ggplot (pie) of the weights of the four assets within the tangency portfolio. Find the 1-day 95% percentage VaR of the tangency portfolio. (d) Plot the efficient frontier + GMVP + tangency portfolio together on one plot.