$($a$)$

How high $($in m$)$ a hill can a car coast up $($engine disengaged$)$ if friction is negligible and its initial speed is $84\mathrm{.}0$ km$/$h$?($Enter a number.$)$

m

$($b$)$

If$,$ in actuality, a $750$ kg car with an initial speed of $84\mathrm{.}0$ km$/$h is observed to coast up a hill to a height $14\mathrm{.}0$ m above its starting point, how much thermal energy $($in J$)$ was generated by friction? $($Enter a number.$)$

J

$($c$)$

What is the average force of friction $($down the slope$)$ if the hill has a slope $2\mathrm{.}5$ above the horizontal? $($Enter your answer in N$.$ Enter a number. Enter the magnitude.$)$

N