A diamond merchant has a chance to buy one of 4 diamonds and wants to sell it immediately. One costs only $1000, but he has a 90% chance of getting $5000 for it (or not selling it at all). The second costs $10,000, and he has a 60% change of selling it for $25,000 (or not selling it at all). The third costs $20,000, but he has a 50% chance of selling it for $60,000 (or not selling it at all). The last diamond costs $50,000, but he has a 1% chance of selling it for $1,000,000 (or not selling it at all). Which diamond gives him the best expected value?