7. In an ultramicroscopic study of silver hydrosol in a cuvette with an area of 5.4 × 10 -12 m 2 and a beam depth of 2.5 × 10 -4 m, 8 cubic particles were counted. Calculate the length of the edge of the particle, if the sol concentration
C = 20 * 10 ^ -2 kg / m 3; the density of silver is ρ = 10.5⋅10 ^ 3 kg / m 3.