You get the mana whether you want it or not. If you don't spend it, it will disappear at the end of the current step (or phase).

The triggered ability isn't a mana ability. It uses the stack and can be responded to.

You get the mana whether you want it or not. If you don't spend it, it will disappear at the end of the current step (or phase).

This is not a mana ability. It uses the stack, and can be responded to.