A box in a certain supply room contains four 40-W lightbulbs,five 60-W bulbs, and seven 75-W bulbs. Suppose that three bulbs arerandomly selected. (Round your answers to four decimal places.)
(a) What is the probability that exactly two of the selectedbulbs are rated 75-W?
(b) What is the probability that all three of the selected bulbshave the same rating?
(c) What is the probability that one bulb of each type isselected?
(d) Suppose now that bulbs are to be selected one by one until a75-W bulb is found. What is the probability that it is necessary toexamine at least six bulbs?
