Farmer Joe Crazyhair has 12.4 acres of land. He uses 4.52 acres of land for growing fruits and 6.15 acres of land for growing vegetables. How many acres are not being used by Mr. Crazyhair? :)

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.