purpose vs the object of the exercise

purpose

noun
  • meaning for existing or doing something. 

  • Resolution; determination. 

  • Function, role. 

  • The end for which something is done, is made or exists. 

verb
  • To have or set as one's purpose or aim; resolve to accomplish; intend; plan. 

  • To have (an) intention, purpose, or design; to intend; to mean. 

the object of the exercise

How often have the words purpose and the object of the exercise occurred in a corpus of books? (source: Google Ngram Viewer )