I need help on this, thank you

Sales for the past 6 months at Dalworth Company are given in the following table: Month Sales July 55 August 64 1:03 September 56 October 38 November 34 December 31 What is the Mean Absolute Deviation (MAD) for August through December forecasts produced by using exponential smoothing with a = 0.8? (Note: Do not round the forecasts, and choose the closest answer.) Multiple Choice O 8.75 O 35.57 9.77 O 15.28