Bacon and Associates, a famous Northwest think tank, has provided probability estimates for the four potential economic states for the coming year. The probability of a boom economy is $15\%,$ the probability of a stable growth economy is $35\%,$ the probability of a stagnant economy is $35\%,$ and the probability of a recession is $15\%.$ The following returns are expected:

Boom: $20\%$ Stable Growth: $10\%$

Stagnant Economy: $5\%.$ Recession: $-10\%$

What is the standard deviation for the stock market?