Most vegans I know are students that live on a very tight budget. The notion that it is expensive to eat vegan is so ridiculous. Sure if you want to eat only beyond burgers or something like that it might be expensive, but nobody does that. Beans, rice, veggies, fruit, there is nothing expensive about that. Sure you don't get heavily subsidized milk for pennies, but you don't realistically need any milk replacements.

As for c, you can do multiple things at once to approach climate change. Especially since they are completly unrelated.