Jack and Jill can weed a vegetable garden in 6 hours working together. It takes Jack 8 hours to weed the garden alone. How long would it take Jill to weed the garden alone? ​

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.