Answer:
the mean would decrease
Explanation:
we can deduce that the outlier is lower than the mean set of numbers, because it the mean is higher with the outlier included. Therefore it's inclusion wouldn't allow for an increase-a and b are not true.
the median's decrease, althoigh could occur due to the additiomal number, it is not always true as the question specifies. this is because there could be the same number below the median, which would give the same value.