a battery company developed a new product. quality engineers found that the life times of the new batteries have a normal distribution with mean 25000 minutes and standard deviation 3000 minutes. to attract new customers, the battery company will give customers full refund if the purchased batteries do not last longer than the minutes stated in the guarantee of the new battery. what is the guaranteed minutes if the battery company expects that 95 percent of the customers who purchase the new batteries will not be eligible for full refund?