World-famous mining mogul Steve Wiley hired the public accounting firm of Joe Wang Associates, PC. to conduct an audit of his new acquisition, Cougar Goldust, Incorporated. The gold inventory was scheduled to be taken on November 30. The perpetual records show only the weight of the gold in various inventory bins. Wang has decided to use a variables sampling approach (difference estimation) to determine the correct weight of gold on hand. Compute the preliminary sample size. The Estimated standard deviation is 25 ounces.