Talk:Trade/@comment-38837689-20190609083031/@comment-38837689-20190609084239

two proofs

https://docs.google.com/spreadsheets/d/16pZ9x-PwvNlIw_rkPKXv9VAnWXUrQ3dG4b8t4HAW9rQ/edit#gid=0

https://docs.google.com/spreadsheets/d/15A8BHdGMUAcmlRhw4EOKOuoZnPxnxmPIBuXHJRwptWo/edit?copiedFromTrash#gid=0