The mean number of shoes a store sells each day is 36 with a standard deviation of 4. What percent of days should the store expect to sell less than 28 pairs of shoes? (Round to the nearest tenth)

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.