What does it mean that Gatsby knew when to stop "? Help ASAP

According to stephen hawking in the "origin of the universe" lecture, "why are we here" and "where did we come from" are questions that

Identify the trade regulation concept described in each scenario. protectionism free trade trade war country a and country b want to develop their respective export markets. both countries have highly developed agricultural, industrial, and service sectors. the countries decide to initially lower trade barriers and eventually remove them completely. arrowright country a has an agrarian economy with an emerging industrial sector. to allow domestic industries to grow, country a applies quotas on all industrial products except those that are used as resources. arrowright country a passes an economic policy that will indirectly give its own companies an advantage over country b’s companies. country b alleges that the policy violates the countries’ trade agreement and imposes retaliatory tariffs. arrowright

Why didn't van gogh knock on breton's door? it seemed imposing and a bit scary. it looked alarmingly middle-class. he couldn't find the door. he saw a book that he liked instead.