If the life, in years, of a television set is normally distributed with a mean of 42 years and a standard deviation of 6 years, what should be the

If the life, in years, of a television set is normally distributed with a mean of 42 years and a standard deviation of 6 years, what should be the guarantee period if the company wants less than 3% of the television sets to fail while under warranty? ( how do you work this problem through ?)