A rectangular waveguide with a = 2b = 4.8 cm is filled with teflon with r

A rectangular waveguide with a = 2b = 4.8 cm is filled with teflon with ε_r =2.11 and loss tangent of 3 X 10^–4. Assume that the walls of the waveguide are coated with gold (σ_C = 4.1 X 10⁷ S/m) and that a TE₁₀ wave at 4 GHz propagates down the waveguide, find: 

(a) α_d, 

(b) α_c.