Long Life Battery Company makes car batteries.After years of product testing, the company knows their batteries follow a normal distribution with a mean lifespan of 45 months and a standard deviation of 7 months.The company guarantees that batteries with a short lifespan will be replaced free of charge.If Long Life 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?

What equation should be used for this problem

z= x or p(x)=(nCx)px 1 p ( )nx or x = + z

or z= x ne) None of the above are correct.