In early $2022,$ United Airlines $($UAL$)$ had a market capitalization of $$14\mathrm{.}3$ billion, debt of $$39\mathrm{.}4$ billion, and cash of $$18\mathrm{.}4$ billion. United also had annual revenues of $$24\mathrm{.}6$ billion. Southwest Airlines $($LUV$)$ had a market capitalization of $$26\mathrm{.}1$ billion, debt of $$12\mathrm{.}3$ billion, cash of $$15\mathrm{.}5$ billion, and annual revenues of $$15\mathrm{.}8$ billion.a$.$ Compare the market$-$capitalization$-$to$-$revenue ratio $($also called the price$-$to$-$sales ratio$)$ for United Airlines and Southwest Airlines.b$.$ Compare the enterprise$-$value$-$to$-$revenue ratio for United Airlines and Southwest Airlines.c$.$ Which of these comparisons is more meaningful? Explain.