The average and standard deviation of

=>

We have (x1+x2+x3+x4)/4 = 5 or x1+x2+x3+x4 = 20.
Since we know the standard deviation of x1, x2, x3, and x4 is 2, we have
((x1 - 5)^2 + (x2 - 5)^2 + (x3 - 5)^2 + (x4 - 5)^2)/4 = ( \(\sqrt{2}\) )^2
=> (x1 - 5)^2 + (x2 - 5)^2 + (x3 - 5)^2 + (x4 - 5)^2 = 8
=> (x1^2 - 10x1 + 25) + (x2^2 - 10x2 + 25) + (x3^2 - 10x3 + 25) + (x4^2 - 10x4 + 25) = 8
=> (x1^2 + x2^2 + x3^2 + x4^2) - 10(x1 + x2 + x3 + x4) + 25 + 25 + 25 + 25 = 8
=> (x1^2 + x2^2 + x3^2 + x4^2) - 10(20) + 100 = 8
=> (x1^2 + x2^2 + x3^2 + x4^2) = 108
=> (x1^2 + x2^2 + x3^2 + x4^2)/4 = 27

Therefore, D is the answer.
Answer: D