What Is the Standard Deviation of a Portfolio Which Is

Multiple Choice

What is the standard deviation of a portfolio which is invested 20% in stock A, 30% in stock B and 50% in stock C?
$\begin{array}{llcc} \text { State of } & \text { Probability of } & \underline{\text { Returns if State Occurs }} \\\underline{ \text { Economy }} & \underline{\text { State of Economy }} & \underline{\text {Stock A\quad Stock B\quad Stock C}} \\ \text {Boom } & 10\% &15\% \quad \quad 10\%\quad \quad 5\%\\ \text { Normal} & 70\%& 9\%\quad \quad 6\%\quad \quad 7\%\\ \text { Recession } & 20\%&-14\%\quad \quad 2\%\quad \quad 8\% \\\end{array}$

A) 0.6%
B) 0.9%
C) 1.8%
D) 2.2%
E) 4.9%