standard deviation of expected returns for HP12c

Does anyone know the keystrokes to calculate this problem on HP? Given the following probability distribution, find the standard deviation of expected returns. Event P(RA) RA Recession 0.10 -5% Below Average 0.30 -2% Normal 0.50 10% Boom 0.10 31%

When calculation expected return and standard deviation with probability like this case, you must use the formula manually. I think it is not so difficult.

that is what I thought. Thanks.