Answer
See below.
Work Step by Step
a) The mean of $n$ numbers is the sum of the numbers divided by $n$.
Hence the mean: $\frac{0.35+0.37+0.41+0.39+0.43}{5}=0.39$
b) The deviation is the difference of the data item and the mean.
Hence here the deviations: $0.35-0.39=-0.04, 0.37-0.39=-0.02, 0.41-0.39=0.02, 0.39-0.39=0, 0.43-0.39=0.04 $
c) The sums of the deviations: $-0.04-0.02+0.02+0+0.04=0$
