The data file inter 2 contains 300 observations of a generated \(\mathrm{I}(2)\) process shown in Figure 12.10. Show that the variable called inter 2 is indeed an \(\mathrm{I}(2)\) variable by conducting a number of unit root tests-first on the level of the data, then on the first difference, and finally on the second difference.

Data From Figure 12.10 :-

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20 20 16 12- +4 60 100 150 200 250 300 FIGURE 12.10 A generated I(2) process.