Jackpot three binders from the store and paid 13.17 if he goes back to the store to purchase five more binders how much in total we have spent on binders

Do one of the following, as appropriate: (a) find the critical value z subscript alpha divided by 2 , (b) find the critical value t subscript alpha divided by 2 . 99%; nequals 17; sigma is unknown; population appears to be normally distributed.