Let p be the total number of people.
Therefore,
[tex]p=4+4+2=10[/tex]Let the number of people that waited for a particular time,x, be n.
Therefore, the probability, Pr(x), that a person waited for a time x is given by
[tex]Pr(x)=\frac{n}{p}=\frac{n}{10}[/tex]Now, we make a table as shown below
x | Number of people(n) | Pr(x) | xPr(x)
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4 | 4 | 0.4 | 1.6
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24 | 4 | 0.4 | 9.6
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106 | 2 | 0.2 | 21.2
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[tex]\text{ The expected value is }\sum \text{xPr(x)}[/tex][tex]\sum \text{xPr(x) = 32.4}[/tex]Therefore, the expected value is 32.4 minutes