# Crossing the River Four people wish to cross a river. They have a boat, but the boat holds at most two people. Each person takes a different amount of time to cross the river; person A takes 20 minutes, person B takes 15 minutes, person C takes 10 minutes, and person D takes 5 minutes. When two people are in the boat, it takes the maximum of their time to cross the river; that is, A and C together would take 20 minutes. What is the smallest crossing time required to get all four people across the river? --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://www.pythonclassroom.com/python-curriculum-map/pedagogy/activities/crossing-the-river.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.