The data set "beersales" has monthly beers sales in millions of barrels. The data can be accessed by doing the following

library(TSA)

data(beersales)

A description can be found by doing

help(beersales)

The following will return the difference between the beersales time series and the lag k of the time series.

diff(beersales,k)

a)The beersales time series is not stationary. Provide a plot of the beersales time series along with an explanation of why the time series is not stationary.

b)Suggest a difference to the time series to make it stationary and provide evidence.