Given data sets: 22.1, 5.7, 18.8, 20.1, 16.1, 13.6, 7.7, 20.5, 20.6, 16.5, 15.0, 11.6, 10.4, 10.1, 14.4, 14.0. Compute σ²−25.
a) 25.5
b) 10.5
c) 15.5
d) 20.5