F = Fg - Fr = m * g * sin alpha - u * m + g * cos alpha
= 70,5 kg * 9,81 N/kg * sin 56,8 - 0,07 * 70,5 kg * 9,81 N/kg * cos 56,8 = 552.2 N
F = m * a
a = F / m = 552.2 N / 70,5 kg = 7,833 m/s^2
s = 1/2 * a * t^2 = 1/2 * 7,833 m/s^2 * (13.9 s)^2 = 756,7 m
W = F * s = 552.2 N * 756,7 m = 417850 J = 417,8 kJ