A Certain Company Makes 12-Volt Car Batteries

Multiple Choice

A certain company makes 12-volt car batteries. After many years of product testing, the company knows that the average life of a battery is normally distributed, with a mean of 44 months and a standard deviation of 7 months. If the company does not want to make refunds for more than 10% of its batteries under the full-refund guarantee policy, for how long should the company guarantee the batteries (to the nearest month) ?

A) 30 months
B) 52 months
C) 35 months
D) 57 months