A Concert Promoter Is Forecasting This Year's Attendance for One

Multiple Choice

A concert promoter is forecasting this year's attendance for one of his concerts based on the following historical data: $$\begin{array} { l l } \text { Year } & \text { Attendance } \\\hline \text { Four years ago } & 10,000 \\\text { Three years ago } & 12,000 \\\text { Two years ago } & 18,000 \\\text { Last Year } & 20,000\end{array}$$ The previous trend line had predicted 18,500 for two years ago, and 19,700 for last year. What was the mean absolute deviation for these forecasts?

A) 100
B) 200
C) 400
D) 500
E) 800