To find the mean rent before the change occurs, we first calculate the mean of the original set of rents: 879, 920, 940, 950, and 990.
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Calculate the sum of the rents: \[ 879 + 920 + 940 + 950 + 990 = 4679 \]
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Divide the sum by the number of tenants (5): \[ \text{Mean} = \frac{4679}{5} = 935.80 \]
So the mean rent before the change is $935.80.
After one tenant's rent changes from $940 to $1115, the new set of rents will be 879, 920, 1115, 950, and 990.
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Calculate the new sum: \[ 879 + 920 + 1115 + 950 + 990 = 4854 \]
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Calculate the new mean: \[ \text{New Mean} = \frac{4854}{5} = 970.80 \]
Thus, the updated means are:
- Before: $935.80
- After: $970.80
Therefore, the best answer is: A. Before $935.80 after $970.80.