A company produces an electric toothbrush with a life (that time period for which it does not need a major repair) that is normally distributed with a mean of 48 months with a standard deviation of 7 months. The company wants to determine the warranty period for the toothbrush. Any toothbrush that fails within the warranty period will be replaced by the company. What should the warranty period be if the company does not want to replace more than 2% of the toothbrushes under warranty