The Neal Company wants to estimate next year’s return

The Neal Company wants to estimate next year’s return on equity (ROE) under different leverage ratios. Neal’s total assets are $14 million, it currently uses only common equity, and its federal-plus-state tax rate is 40%. The CFO has estimated next year’s EBIT for three possible states of the world: $4.2 million with a 0.2 probability, $2.8 million with a 0.5 probability, and $700,000 with a 0.3 probability. Calculate Neal’s expected ROE, standard deviation, and coefficient of variation for each of the following debt ratios; then evaluate the results:
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What is the formula for solving standard deviation and variance? I completed the expected ROE, but I’m not sure how to solve for the other two.