Explain what are the differences between Incomplete Contracting Theories of the nature of the Firm and Principal-Agent Theories?

Question:
Explain what are the differences between Incomplete Contracting Theories of the nature of the Firm and Principal-Agent Theories?

Link to the lecture: https://drive.google.com/open?id=11Ch4lf1joGn1aW1nuddk6r9W0OiQKd4X