Plot the following risky portfolios on a graph:

a$)$ Which of these portfolios are efficient? Which portfolios are inefficient?

b$)$ Suppose you can also borrow and lend at an interest$-$rate of $10$ percent. Which of the above portfolios is the best one?

c$)$ Suppose you are prepared to tolerate a standard deviation of $15$ percent. What is the maximum expected return that you can achieve if you cannot borrow nor lend?

d$)$ What is your optimal strategy, if you can borrow or lend at $10$ percent and are prepared to tolerate a standard deviation of $15$ percent? What is the maximum expected return that you can achieve?