Only one, but they get three tech. reports out of it.
or
Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
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It's not a shrub, it's a lemon tree my dear Watson.
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Because they don't fit on a ironing board
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proving once and for all that you can't have your kayak and heat it.
or