$1.$ What is the difference between firm$-$specific risk and unsystematic risk?

$2.$ Explain why diversification reduces unsystematic risk but not systematic risk.

$3.$ Explain what happens to the standard deviation of returns of a portfolio as the number of stocks in the portfolio increases.

$4.$ Enrique owns five stocks: Alaska Airlines, American Airlines, Delta Airlines, Southwest Airlines, and Ford. Radha also owns five stocks: Apple, McDonald$$s$,$ Tesla, Facebook, and Disney. Does Enrique or Radha have a more diversified portfolio?

$5.$ You are considering purchasing shares in a company that has a beta of $0\mathrm{.}8.$ Explain what this beta means.