Uppose the lifetime (in months) of certain type of battery is a random variable with pdf In a random sample of 4 such batteries, what is the probability that at least 2 of them will work for more than 6 months (round off to second decimal place)

Several paint mixtures are made by mixing blue paint and white paint. paint colors blue paint white paint mixture a 5 cups 12 cups mixture b 6 cups 6 cups mixture c 4 cups 12 cups mixture d 5 cups 6 cups which mixture has the highest ratio of blue paint to white paint