your computer should have a calculator able to multiply HEX values.
If not, then there are many HEX calculators that can be installed on your computer.
Why are you asking this question here? Don't seem that you should ask the author of the book? If this exercise is purposed to teach HEX calculations, there is the answer, otherwise could be: Do as you feel confortable; For me, dealing with dozens 1's and 0's is boring and hard to review, as well as it increase the chance to mistake.