Work, Energy and Power

A woman pushes a trunk on
a railway platform which has a rough
surface. She applies a force of 100 N over a
distance of 10 m. Thereafter, she gets
progressively tired and her applied force
reduces linearly with distance to 50 N. The
total distance through which the trunk has
been moved is 20 m. Plot the force applied
by the woman and the frictional force, which
is 50 N versus displacement. Calculate the
work done by the two forces over 20 m.