A savings account, which started with a balance of $500, has the following end of year balances: Year 1 = $550; Year 2 = $580; Year 3 = $660; Year 4 = $772; Year 5 = $950. No withdrawals were made over the life of the account, but there was one additional deposit of $50 made at the beginning of year 5. If the account earned a total of $300 in simple interest over its life, how much was earned in interest on interest?