Consider the following table, consisting of 20 observations of the variable y and time t. The data are also on the text website, labeled Exercise 18.12
![204_observations of the variable.png](https://secure.tutorsglobe.com/CMSImages/204_observations of the variable.png)
a. Plot the series along with the superimposed linear and quadratic trends. Which trend model do you think describes the data well?
b. Estimate a linear trend model and a quadratic trend model. Validate your guess from the graphs by comparing their adjusted R2.