As a rule of thumb, the sampling distribution of the sample proportions can be approximated by a normal probability distribution whenever ... (One answer only) (1 point) a. np 5 b. n(1-P) 25 and n 30 c. n30 and (1-p) =0.5 d. None of these alternatives is correct. Our company's machine is designed to fill cereal boxes with an average 18 ounces of cereal with a standard deviation of 2 ounces. Show your detailed calculations to find the upper and lower control limits if samples of 49 boxes were inspected. (Manually solve, no Excel) (3 points)