At a large company in Alberta, a box in a certain supply room contains 4 40-W lightbulbs, 7 60-W lightbulbs, and 4 75-W bulbs. Suppose that 3 bulbs are randomly selected without replacement. (Round your answers to 4 decimal places, if needed.) (a) What is the probability that exactly two of the selected bulbs are rated 75-W?

Your last answer was interpreted as follows:

0.14510.1451

(b) What is the probability that all three of the selected bulbs have the same rating?

Your last answer was interpreted as follows:

0.09450.0945

(c) What is the probability that one bulb of each type is selected?

Your last answer was interpreted as follows:

0.24620.2462

(d) Suppose now that bulbs are to be selected one by one until a 75-W bulb is found. What is the probability that it is necessary to examine at least six bulbs?