Use the Data Given Below to Answer the Following Question(s)

Use the data given below to answer the following question(s) .
The table provided below gives the sales details of the number of android smart phones at an electronic retail store for the past 6 weeks.The time series appears to be relatively stable, without trend, seasonal, or cyclical effects.The value of k is set at 3.(Hint: Optimize α value.)
$\begin{array}{|c|c|}\hline \text { Week } & \text { Units sold } \\\hline 1 & 88 \\\hline 2 & 44 \\\hline 3 & 54 \\\hline 4 & 65 \\\hline 5 & 72 \\\hline 6 & 85 \\\hline\end{array}$
-Which of the following is the value of the root mean square error for the given data?

A) 11.56
B) 21.72
C) 13.87
D) 20.13