In 1990, Mrs. John Hay Whitney sold her painting by Renoir, Au Moulin de la Galette, depicting an open-air Parisian dance hall, for $71 million. The buyer also had to pay the auction house commission of 10% or a total of $78.1 million. The Whitney family had purchased the painting in 1929 for $165,000. What rate of return did Mrs. Whitney receive on the investment