The label on 1-gallon cans of paint states that the amount of paint in the can is sufficient to paint 400 square feet. However, this number is quite variable. In fact, the amount of coverage is known to be approximately normally distributed with a standard deviation of 25 square feet. How large a sample should be taken to estimate the true mean coverage of all 1-gallon cans to within 5 square feet with 95% confidence?