A mechanic sells a brand of automobile tire that has a life expectancy that is normally​ distributed, with a mean life of 25,000 miles and a standard deviation of 2500 miles. He wants to give a...

A mechanic sells a brand of automobile tire that has a life expectancy that is normally​ distributed, with a mean life of 25,000 miles and a standard deviation of 2500 miles. He wants to give a guarantee for free replacement of tires that​ don't wear well. How should he word his guarantee if he is willing to replace approximately​ 10% of the​ tires?

tires that wear out by _____ miles will be replaced free of charge. round to nearest mile.