PLEASE HELP

1.

The lifetime of a certain brand of automobile batteries has a mean of 2% years and standard deviation of 6 months. Recently, the manufacturer of this brand of batteries has received a rash of complaints from unsatisfied customers whose batteries have died earlier than expected. In light of these complaints a consumer group samples n of these batteries and subjects them to tests that determine battery life. If n : 16, then what is the probability that mean lifetimes is 52 months or fewer? An electrical firm manufactures light bulbs that have their lifetimes (approximately) normally distributed, with mean of 800 hours and variance of 1600 hours2 Consider a random sample of 16 bulbs manufactured by this firm. The probability of total lifetime exceeding 12400 hours is