a$)$ Explain the difference between systematic risk and unsystematic risk with that aid of the graph.

b$)$ Musonda currently has a portfolio of shares giving a return of $22\%$ with a risk of $14\%.$ He is considering a new investment which gives a return of $23\%$ with a risk of $15\%.$ The coefficient of correlation of the new investment with his existing portfolio is $+0\mathrm{.}2.$ The new investment will comprise $45\%$ of his enlarged portfolio.

Calculate the portfolio risk and expected return if Musonda goes ahead with the new investment? with references