$\"\"$

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The function of the probability is $\"\"$ .

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Where $\"\"$ represents the number of minutes.

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(a)

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How many minutes are needed for the probability to reach $\"\"$ .

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Therefore, $\"\"$

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$\"\"$

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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From the definition $\"x$ if and only if $\"y$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ minutes are needed for the probability to reach $\"\"$ .

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$\"\"$

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(b)

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How many minutes are needed for the probability to reach $\"\"$ .

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Therefore, $\"\"$

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$\"\"$

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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From the definition $\"x$ if and only if $\"y$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ minutes are needed for the probability to reach $\"\"$ .

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$\"\"$

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(a) $\"\"$ minutes are needed for the probability to reach $\"\"$ .

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(b) $\"\"$ minutes are needed for the probability to reach $\"\"$ .