(Expected return and risk) The following data represent returns for the common stocks over a one-year period.

Probability	Returns
	Google	ATT
0.1	-20%	-10%
0.2	8%	4%
0.2	12%	37%
0.3	-18%	20%
0.2	4%	-6%

The standard deviation of Google return is _%. (Keep the sign and two decimal numbers.)