Answer:
Expected returns = (return with healthy economy x probability of healthy economy) + (return with soft economy x probability of soft economy) + (return of recessive economy x probability of recessive economy) = (30% x 0.7) + (10% x 0.2) + (-25% x 0.1) = 20.5%
Variance = (30² x 0.7) + (10² x 0.2) + (-25² x 0.1) - 20.5² = 630 + 20 + 62.5 - 420.25 = 292.25
Standard deviation = √292.25 = 17.095 = 17.1%