Centerville Bikes and Stuff $(CBS)$ sells motorcycles and accessories. The number $of$ helmets sold $byCBS$ per week for the past six weeks follows.

Month $123456$

Value $191416121815$

Use $=0\mathrm{.}2to$ compute the exponential smoothing values for the time series.

Compute MSE. $(Round$ your answer $to$ two decimal places.$)$