A large bag of seeds contains three varieties in the ratios 4:2:1 and their germination rates are 50%, 60% and 80% respectively. Show that the probability that a seed chosen at random from the bag will germinate is 4. Find, to three decimal places, the probability that of four seeds chosen at random from the bag, exactly two of them will germinate. Given that 150 seeds are chosen at random from the bag, estimate, to three decimal places, the probability that fewer than 90 of them will germinate. (L)