Cyclone Efficiency

I have a problem where I've been asked to find the cut diameter for a set of cyclones. The equation I plan to use is Dpc = (ln2/M)^(n+1) I know n=0.945 but need to calculate M in order to find Dpc. The grade efficiency for a particle size Dpi = 3 x 10^-6m is 0.6536. So, I should be able to calculate M from the equa ...continues