Can someone help me please?? You buy 3 pairs of jeans for $35.95 each and get a fourth pair for free. What is your cost per pair of jeans?

Aproduction manager test 10 toothbrushes and finds that their mean lifetime is 450 hours. she then design sales package of this type of toothbrush. it states that the customers can expect the toothbrush to last approximately 460 hours. this is an example of what phase of inferential statistics