Estimated time: 10-15 hours
Actual time spent: 12.5 hours; 2 hours spent coding the actual methods, and 10.5 hours setting up the environment and testing

To test the ConsoleApp, I used the System.IO.Abstractions package to mock a file system and run automatic tests on my methods. Therefore, to test my code, the System.IO.Abstractions package will need to be installed.

More information on the package here: https://www.nuget.org/packages/System.IO.Abstractions

Once System.IO.Abstractions is installed, you should be able to run the UnitTest1.cs file under the directory TestLetterService.