Cloud seeding has been studied for many decades as a weather modication procedure. The rainfall in acre-feet from 20 clouds that were selected at random and seeded with silver nitrate follows, 18.0, 30.7, 19.8, 27.1, 22.3, 18.8, 31.8, 23.4, 21.2, 27.9, 31.9, 27.1, 25.0, 24.7, 26.9, 21.8, 29.2, 34.8, 26.7, and 31.6. Assume this sample data follows a normal distribution. (a) Assume that the true standard deviation of the rainfall is a = 4. Can you support a claim that mean rainfall from seeded clouds exceeds 25 acre-feet. Use a = 0.01. (b) Now assume you don't know the true standard deviation. Can you support a claim that mean rainfall from seeded clouds exceeds 25 acre-feet. Use a = 0.01. Find the p- value