`main()` should return type Result<f32, Error> instead of f32.

[sawshep]

This would also allow answer to go uninitialized, as if it was never initialized with a value, you can just return Err(e).
Right now the value is set to 404.0, which is misleading.

[wizardwatch]

I am working on fixing that. I am going to write a custom error message that will come with my unit test commit. Thank you for bringing up the issue.