In $2022,$ the total air freight revenue of United Airlines is $$2,013\mathrm{.}5$ million. It carried a total of $601\mathrm{.}6$ million kg of air freight, and its freight revenue$-$ton$-$miles is $2,818$ million. What is the air freight yield for United Airlines in $2022?$

Group of answer choices

a$.$ $$4\mathrm{.}68$

b$.$ $$3\mathrm{.}35$

c$.$ $$1\mathrm{.}40$

d$.$ $$0\mathrm{.}71$