It is raining outside, so a student lifts their textbook vertically 1.2 meters above
their head with a force of 42 Newtons to keep themselves dry. What is the work
done on the textbook? Is any additional work done on the textbook when the
student begins to walk horizontally?

Work done is  50.4J.

Explanation:

The work done by the student in lifting the book 1.2 meters vertically is

When the student begins to walk horizontally, the net force on the book is zero (gravity is pulling it down, the student is lifting it up). Thus, although the student is displacing the book horizontally, but because no force is exerted on it, the work done is zero.