I need help

New Wave manufactures and distributes computer terminals and equipment for the rapidly growing data transmission industry. Because it faces intense competition, its new products may or may not be competitive in the marketplace, so its future earnings cannot be predicted very well. The rate of return and probability distribution for the company are shown here:

Calculate:

1. Expected rate of return.
2. Standard deviation.
3. Coefficient of variation.

\begin{tabular}{|l|c|c|} \hline Demand for the & Probability of this & Rate of return if this \\ \hline company's products & demand occurring & demand occurs \\ \hline Weak & 0.1 & (50%) \\ \hline Below average & 0.2 & (5) \\ \hline Average & 0.4 & 16 \\ \hline Above average & 0.2 & 25 \\ \hline Strong & 0.1 & 60 \\ \hline \end{tabular}