Coyote Cable Has Been Experiencing an Increase in Cable Service

Coyote Cable has been experiencing an increase in cable service subscribers over the last few years due to increased advertising and an influx of new residents to the region.The number of subscribers (in 1000's)for the last 16 months are as follows: $$\begin{array} { c c | c c | c c } \hline \hline \text { Month } & \text { Sales } & \text { Month } & \text { Sales } & \text { Month } & \text { Sales } \\\hline 1 & 12.8 & 7 & 20.6 & 12 & 23.8 \\2 & 14.6 & 8 & 18.5 & 13 & 25.1 \\3 & 15.2 & 9 & 19.9 & 14 & 24.7 \\4 & 16.1 & 10 & 23.6 & 15 & 26.5 \\5 & 15.8 & 11 & 24.2 & 16 & 28.9 \\6 & 17.2 & & & & \\\hline \hline\end{array}$$ Forecast the number of subscribers for months 17,18,19,and 20.