in the second pic, can please help me figure out how the profile return percentage of the standard deviation is 3.9?? like how and why is it 3.9???

Risk and DIY Diversification 13 of 9). Two Asset Example: Gold imple: Gold and Auto stocks Probability Rate of Retur Auto Stock Gold Stock Scenario Recension Normal Boom 20 1/3 Deviation from Rate o Return Sound Dovlation 20 Scenario Recession Normal Boom Expected return +18 +13 -B+B + 16) - 58 Variance (169 + 0 + 100) - 112.7 001-4-4411 - 2007 2887 - 1645 112.7 - 10.6% Standard deviation (V varianco) Two Asset Example (continued) Assume 25% in Gold and 75% in Auto Probability 1/3 1/3 Rate of Return, % Auto Stock Gold Stock -8 +20 +5 -20 Scenario Recession Normal Boom Expected return Variance Standard deviation Portfolio Return -1.0 +4.5 +8.5 +3 1/3 +18 112.7 10.6 268.7 16.4 15.2 3.9