Answer:
A) it increases the mean value of the prizes
Explanation:
Adding a number to a data set that is higher than the mean of that data set will increase the mean. Since all of the other prizes have a value less then $100, their mean value is less than $100. Adding the $100 prize will increase the mean value of prizes.
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If you go to the trouble to see if any of the "median" answers work, you find that the median prize value is a $5 meal. There is a sufficiently large number of those that adding one more prize that is not a $5 meal will not change the median.