For #3 and #4 use the NS eqns as given in the Class Notes handed out.
The definitions of kappa and mu are given there.   Both of these 
coefficients are diffusion coefficients and are of the order of lambda*nu, 
lambda is the mean free path and nu is the collision frequency.  The NS 
equations are valid only if lambda << L.   Note also that lambda, nu, and 
the thermal speed vth are related by vth = lambda*nu.