Using the concept of complementary probabilities, it is found that:
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Item a:
Thus:
[tex]p = 1 - 0.4 = 0.6[/tex]
0.6 = 60% probability that at least three purchase the electric oven.
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Item b:
The probability of all the same type is:
[tex]p = 0.007 + 0.104 = 0.111[/tex]
Thus, the probability of at least one of each type is:
[tex]p = 1 - 0.111 = 0.889[/tex]
0.889 = 88.9% probability that one of each type is purchased.
A similar problem is given at https://brainly.com/question/24622191