Every Normal model is defined by its parameters, the mean and the standard deviation. For each model described below, find the missing parameter. As always, start by drawing a picture. a) = 18, 40% above 40; o = ? Choose the correct graph below. O A. OB. OC. OD. 18 40 40 18 u= 18, 40% above 40; o= ? Find the standard deviation. G= (Round to one decimal place as needed.) b) u = 91, 8% below 55; a=? Choose the correct graph below. O A. OB. OC. OD. 91 5 Click to select your answer(s).