John Whitney Payson, who purchased a painting by Vincent van Gogh for $80,000 in 1947, sold it for $53.9 million in 1988. If Mr. Payson had invested his $80,000 in another investment vehicle (such as stock), how much annual interest would he need to have earned in order to accumulate the same wealth as he did from the painting investment? Assume for simplicity that the investment period is 40 years and that the interest is compounded annually.