Answer
The car reaches a highest point of 25.4 meters above the bottom of the hill.
Work Step by Step
We can use conservation of energy to find the highest point the car reaches on the hill (where we can assume that the kinetic energy is zero):
$U_2+KE_2 = U_1+KE_1$
$mgh_2+0 = mgh_1+\frac{1}{2}mv_1^2$
$h_2 = h_1+\frac{v_1^2}{2g}$
$h_2 = (5.0~m)+\frac{(20.0~m/s)^2}{(2)(9.80~m/s^2)}$
$h_2 = 25.4~m$
The car reaches a highest point of 25.4 meters above the bottom of the hill.
