Answer
$(a)\space 25.1\space m/s$
$(b)\space 107.2\space hp$
Work Step by Step
Please see the attached image first.
Let's apply the equation $F=ma$ to the car,
$\angle11.8^{\circ}\nearrow F=ma$ ; Let's plug known values into this equation.
$F-1590g\times sin11.8^{\circ}=0$
$F=3186\space N$
Let's apply equation $P=FV$ to the car,
$P=FV$ ;Let's plug known values into this equation.
$88\space kW=3186\space N\times V$
$88\times10^{3}\space kgm^{2}/s^{3}=3186\space kgm/s^{2}\times V$
$25.1\space m/s=V$
(b) We know that $1\space hp= 746\space W,$ So we can multiply the value by 1 hp/746W to get the horsepower of the car,
$80\space kW= 80\times10^{3}W\times (\frac{1\space hp}{746\space W})=107.2\space hp$
