Question 1138417
z>(x bar-mean)/sigma/sqrt (n)
z>(23-25.1)*6/6.4
z>-1.96875
0.9755 is correct

z for the 90th percentile is 1.28
1.28=(x bar-mean)/sigma/sqrt (n) or (x bar-mean) divided by 6.4/6, which is 1.067
8.19=6(x bar-mean)
1.367=x bar-mean
x bar=26.467 min