Reference 1 in the Wheat and Chessboard Wikipedia page lists an article entitled "A Penny Doubled Every Day for 30 Days = $10.7M". It turns out that $10.7M is an approximate total. Using your compound_by_period function, compute exactly how much money you would have if you started with a penny ($0.01) and doubled it every day for 30 days. Assign this total after 30 days to a variable named total_after_30