a$)$ Explain the following concepts in portfolio theory

i$)$ Efficient set theorem

ii$)$ Unsystematic risk

iii$)$ Optimal portfolio

b$)$b$)$Mr$.$ Sam intends to create a portfolio that consists of a corporate bond fund, A$,$ and a common stock fund, B$.$ For a sh$\mathrm{.}1,000,000$ investment, the expected return for A is sh$.75,000$ and the expected return for B is sh$100,000.$ The variance for A is $6\%$ and the variance for B is $10\%.$ The covariance of A and B is $-115.$

i$)$Compute the portfolio expected returnif he invests sh$.200,000$in the corporate bond fund and sh$\mathrm{.}300,000$ in the common stock fund.

ii$)$Compute the portfolio risk if he invests sh$.200,000$ in the corporate bond fund and sh$.300,000$ in the common stock fund.