A deeper issue
The ACs who each tell of Gf and sister not wanting to accept the solution given comes to the heart of a bigger issue here.
We seem to have got ourselves into a world where it's considered OK to accept truth only when it's convenient. You want to believe that Brexit will make things better for ordinary working folk, that certain fruits will make you healthy and cure cancer, that the Universe is just 6000 years old. Well that's all OK in 2017. Facts are optional.