The thickness of a plastic film (in mils) on a substrate material is thought to be influenced by the temperature at which the coating is applied. A completely randomized experiment is carried out. Eleven substrates are coated at 125 F resulting in a sample standard deviation of s = 11.6. Another 13 substrates are coated at 150 F, resulting in s = 20.3. Is there sufficient evidence to conclude that the two population variances differ? (a) Test the hypothesis Ho H H = 0 vs Ho H - > 0. Calculate fo= Round your answer to three decimal places (e.g. 98.765). (b) Is there sufficient evidence to conclude that the two population variances differ? Use a = 0.01.