A gigantic warehouse stores more than 60 million empty aluminum beer and soda cans. Recently, a fire occurred at the warehouse. The smoke from the fire contaminated many of the cans with blackspot, making them unusable. A statistician was hired by the insurance company to estimate the proportion of cans in the warehouse that were contaminated by the fire.

How many aluminum cans should be randomly sampled to estimate the proportion to within 0.04 with 95% confidence?