How to compute the time window in model deployment?

Every time I input the code for the problem I get NA. Am I doing something wrong and is there some other dataset I am supposed to be using?
I understand this by hand but don't know if I am missing something.

Thanks for helping.

Nicola Shorten

Answers and follow-up questions

Answer or follow-up question 1

Hi Nicola,

You don't need to use a dataset. If you need to use data if will be mentioned in the question.
Yes you can solve it by hand. If you do it in R (and hence show your approach) you can get partial credit if your answer is not 100%

Michel Ballings

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