In early $2015,$ Ford Motor$($F$)$ had a book value of equity of $ $24\mathrm{.}4$billion$,3\mathrm{.}4$ billion shares$$ outstanding, and a market price of $ $15\mathrm{.}55$ per share. Ford also had cash of $ $21\mathrm{.}6$billion$,$ and total debt of $ $117\mathrm{.}5$ billion. Three years$$ later, in early $2018,$ Ford had a book value of equity of $ $35\mathrm{.}4$billion$,4\mathrm{.}9$ billion shares outstanding with a market price of $ $10\mathrm{.}39$ per$$ share, cash of $ $26\mathrm{.}1$billion$,$ and total debt of $ $154\mathrm{.}7$ billion. Over this$$ period, what was the change in$$ Ford's

a$.$ market$$ capitalization?

b$.$ market$-$to$-$book ratio?

c$.$ enterprise$$ value?