i have calculated value of kn, on the base of kn value, cm should be calculated. kn conditions are given below. how to use this condition and get result?

If Kn<.01 cm=((2*eta*r)/(3*tau*delta))*((8*M)/(pi*R*T); If 0.01<kn<1 cm=((eta)/(tau*delta))*((p*D)/(pa))*((M)/(*R*T)); If kn>1 cm=((3*tau*delta)/(2*eta*d))*(((pi*R*T)/(8*M))^(0.5))+(((tau*delta)/(eta))*((pa)/(p*D))*((R*T)/(M))))^(-1);