Question

In the sport of skeleton a participant jumps onto a sled (known as
a skeleton) and proceeds to slide
down an icy track, belly down and
head first. In the 2010 Winter
Olympics, the track had sixteen turns
and dropped 126 m in elevation from
top to bottom. (a) In the absence of
nonconservative forces, such as friction and air resistance, what would be
the speed of a rider at the bottom
of the track? Assume that the speed at
the beginning of the run is relatively
small and can be ignored. (b) In reality, the gold-medal winner (Canadian
Jon Montgomery) reached the bottom
in one heat with a speed of 40.5 m/s
(about 91 mi/h). How much work was
done on him and his sled (assuming a
total mass of 118 kg) by nonconservative forces during this heat?
I successfully finished part a.) and came up with Vf=49.7m/s. Part b.)is where I need help.

Answer 1

b. work done (masshim+masssled)g*heightfell

Answer 2

Is that the PE which is conservative? The book states -4.89x10^4 J as the answer. The one proposed above yields -145706.4J.
Could the book be wrong?