Answer: C
Step-by-step explanation:
Mean is 10(.27)+20(.28)+30(.45) = 21.8
So standard deviation [tex]=\sqrt{(10-21.8)^{2} \cdot 0.27+(20-21.8)^{2} \cdot 0.28+(30-21.8)^{2} \cdot 0.45} \approx 8.29[/tex]
