1. (Exact) The average active-ingredient yield per liter of raw material for samples of vials may be approximated by a normal distribution with mean u 30 grams and standards deviation a 0.2 gram. Find the probability that the average yield of a sample of size 9 is 4 Stat 319-16(212) Page 6 a. less than 29.55 grams. b. between 29.5 and 30.25 grams c. greater than 30.45 grams d. between 30.15 and 30.35 grams. e. Find the 20th and the 90th percentiles. Interpret them