After some study of the economy, your forecast for next year is that a boom economy has a 30% chance of occurring, a neutral economy 50%, and a bust economy a 20% chance of occurring. You also estimate that a certain stock would have a return of 31% in a boom economy next year, 15% in a neutral economy , and -13% in a bust economy. The risk-free rate is 4.9%. What is the standard deviation of expected returns for this stock next year? (Answer to the nearest tenth of a percent, but do not use a percent sign).

Probability

Return

Boom Economy

30% 31%

Neutral Economy

50% 15%

Bust Economy

20% -13%

Selected Answer:14.2

Correct Answer:15.3 0.1

Can someone show me how to put this in excel? I dont know how to work the problem I keep getting it wrong.