Question 906434
Let Upper X be the number of years before a particular type of machine will need replacement. Assume that Upper X has the probability function 
f(1) = 0.3
f(2) = 0.1
f(3) = 0.2
f(4) = 0.1
f(5) = 0.3
Find the probability that the machine needs no replacement during the first 3 years.
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P(no replacement in 1st 3 years) = 1 - (0.3+0.1+0.2) = 0.4
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Cheers,
Stan H.