Imagine that the same waveguide as above is now filled completely and homogeneously with a dielectric foam material instead of air. The material has a dielectric constant of $1\mathrm{.}8.$ What is the cutoff frequency of the dominant mode $($the TE mode$)$ of the waveguide in this new scenario? Type your answer in GHz to three places after the decimal. Hint: Assume for this geometry that the cutoff wavenumber has the same value independent of the material filling the guide.