5.16 An air-filled rectangular waveguide is designed to transmit signals in the TE,g mode in the frequency band 5 GHz to 10 GHz. The waveguide is then filled with a

material with relative dielectric constant equal to 4. In which of the following frequency bands can this waveguide be used to transmit a signal? (a) 20 GHz to 40 GHz (b) 10 GHz to 20 GHz (c) 1.25 GHz to 2.5 GHz (d) 2.5 GHz to 5 GHz