Conversation so far:
What did Yunus joined after graduation?
After his graduation, Yunus joined the Bureau of Economics as a research assistant to the economics researches of Professor Nurul Islam and Rehman Sobhan.
What did Muhammad Yunus published from his home in Nashville?
Muhammad Yunus also published the Bangladesh Newsletter from his home in Nashville.

Question: What did he developed in 1975?
Self-contained rewrite: What did Muhammad Yunus develope in 1975?