Bruce invested $12,000 in a mutual fund five years ago. He received a dividend check for $1,000 after the first year. He received $750 after the second year. At the end of the third year, he received a check for $1,500. After the fourth year, he collected $750. His final dividend check of $1,000 was received at the end of the fifth year. Assume that Bruce sold the mutual fund at the end of the fifth year for $18,000. What was Bruces internal rate of return on this investment?