125. Solving a chemistry problem

From the electron microscopic analysis of a sample of silver nanoparticles, the distribution of the number of particles N over the diameter d is found, shown in the table below (for the corresponding problem number). Calculate (for your problem number) the arithmetic mean diameter d, the standard deviation of the diameter s and the coefficient of variation V (in percent).
Problem 18
d, nm 7.38 7.70 8.03 8.35 8.67 8.99 9.31 9.64 9.96 10.28 10.60 10.93 11.25 11.41
N 1 2 2 6 14 15 15 30 26 24 22 23 13 3