b) enjoyable

In my head, I was assuming motivation, edited to clarify.

Most people don't get past algebra.

Yeah I know, that's why I commented. Even basic facility in proof based math is an extremely powerful mental technology, as I tried to say. I would not recommend calculus. I am talking about combinatorics or graph theory, or discrete math in general, where you can see the basic building blocks of proofs and proof strategies. This is worth years of effort.