The [math]:: accelerator allows us to use the methods of the System.Math class. The Round() method accepts one or two arguments; in case of a single argument, the rounding happens to the nearest integer. The optional second parameter specifies the number of digits after the decimal point.

The Pow() method is almost self-explanatory: 1024² in our case. The Floor() method brought down numbers from 30.00 to less than 31, down to 30.

This is what we did:

1. Listed out the files to delete: we subtracted the LastWriteTime from today, and performed a Floor operation on it since we were not allowed to use the -and operator.
2. Displayed the files.
3. We performed a remove operation on each of the files, while also adding the size of each of the files to $TotalFileSize.
4. In the end, we divided $TotalFileSize by 1024² and rounded it off to the nearest MB.